Chemical changes in calcium arsenate during storage

Historic, archived document

Do not assume content reflects current
scientific knowledge, policies, or practices.

UNITED STATES DEPARTMENT OF AGRICULTURE

BULLETIN No. 1115 ¥&

Washington, D. C. Vv November 28, 1922

CHEMICAL CHANGES IN CALCIUM ARSENATE
DURING STORAGE.

By C. C. McDonnett, Chief, and C. M. Smiru, Assistant Chemist, Insecticide and
Fungicide Laboratory, Miscellaneous Division, Bureau of Chemistry, and B. R.
Coap, Entomologist in Charge, Delta Laboratory, Bureau of Entomology.)

CONTENTS.

Page Page
furpose of investigation......................- Pa DISCUSSIONS £2 AG.e oars os ett te ina ce eee 23
Results of previous investigations... .. ase ey SM eSTEETPOIRDY.. «222 oA PSS) we ee 27
Results of present investigation................ 3 |

PURPOSE OF INVESTIGATION.

Soon after calcium arsenate had been introduced into the Cotton
Belt for use in the control of the cotton boll weevil, the United States
Department of Agriculture began to receive complaints of injury to
cotton plants resulting from the application of this material. Chemi-
cal analyses showed that much of the calcium arsenate being used
in the cotton-growing region at that time contained from 1 to 5 per
cent of ‘ water-soluble”’ arsenic oxid,? which explained to some extent
the injury that was being done to the plants.

In an endeavor to place the responsibility for this unsatisfactory
condition, it was suggested that perhaps commercial calcium ar-
senates deteriorated somewhat when stored for a period of several
weeks or months and that this deterioration was more rapid under
the climatic conditions existing in the cotton-growing States. This
problem was a very serious one, not only from the standpoint of the
consumer but from that of the manufacturer as well, for on its
solution depended the answer to the question whether or not it was

1L. N. Markovitz and A. Shaver, junior chemists, of the Bureau of Chemistry, assisted in the analytical
work, and T. P. Cassidy and M. T. Young, of the Bureau of Entomology, cared for and sampled all the
material stored at Tallulah, La.

2 As determined by the official method of the Association of Official Agricultural Chemists, J. Assn.
Offic. Agr. Chemists, 5 (1921): 37.

3835°—22—_1

~ and Haag,® the only workers who have considered the question of a

2 BULLETIN 1115, U. S. DEPARTMENT OF AGRICULTURE.

safe to use calcium arsenate that had been stored for any appreciable
length of time. A preliminary investigation showed that in the |
cases of the most serious burning reported, the injury was due to the
use of improperly made calcium arsenate. The evidence of deteriora-
tion seemed sufficiently suggestive, however, to warrant an investiga-
tion of the matter under accurately controlled conditions.

RESULTS OF PREVIOUS INVESTIGATIONS.

Robinson? showed that chemical changes occur in calcium arse-
nate through the action of carbon dioxid in the presence of water and
stated that under atmospheric conditions a similar but much slower
action probably would occur. As a result of bubbling carbon)
dioxid through suspensions of dicaletum and tricalcium arsenates
in water, he concluded that there was an evident “solvent action
upon the calcium arsenates.’’ However, while this writer’s results for
tricalcium arsenate were higher, those for dicalcium arsenate were }
lower than his figures for the solubility of the same salts in pure |
water. |

Patten and O’Meara‘ suggested that calcium arsenate when |
applied to foliage would almost certainly be subject to change by |
the carbon dioxid given off by the leaves. In pursuance of this
idea, they determined the amount of arsenic rendered soluble when
saturated carbon dioxid water was used in place of distilled water
in the regular method for determining water-soluble arsenic oxid in
calcium arsenate. The six samples used by them gave an average —
of 0.7 per cent soluble arsenic oxid with distilled water and an aver-—
age of 18.5 per cent soluble arsenic oxid with the carbonated water. |

The work of the previous investigators was done in connection
with the action of carbon dioxid on calcium arsenate when applied
to foliage in a thin film and subjected to the effect of moisture. Reedy |

possible change in calcium arsenate during storage, state that “dur-
ing storage this product undergoes some change in composition which
results in a considerable increase in the amount of water-soluble arse-
nate.” They thought at first that moisture and carbon dioxid from
the air caused this change, but state that ‘‘the use of air-tight con-
tainers has not been sufficient to prevent it.’’ However, they report —
experiments showing that exposure to laboratory air and to moist
carbon dioxid caused an increase in the water-soluble arsenic which
in the latter case was quite marked. As a result of their work, they
conclude that ‘‘the decomposition of tricalcium arsenate is due to
hydrolysis, which seems to be catalyzed by many substances that —
3 J. Agr. Research, 13 (1918): 288; Oregon Agr. Col. Exp. Sta. Bull. 131 (1918), p. 10.

4 Mich. Agr. Col. Exp. Sta., Quart. Bull., Nov., 1919, p. 83.
5J. Ind. Eng. Chem., 13 (1921): 1038.

CHEMICAL CHANGES IN CALCIUM ARSENATE. a.

may be present as impurities.”’ The results presented are not
sufficient to substantiate this conclusion in so far as it applies to
deterioration during storage.

RESULTS OF PRESENT INVESTIGATION.

The United States Department of Agriculture recommends the
application of calcium arsenate on cotton only in the form of a dust.
All of the work here reported, therefore, was done on calcium arsenate
in the dry powdered form.

It was realized that if chemical changes occur in calcium arsenate
during storage, the type of container in which it is stored, as well as
the original composition of the material and the climatic conditions
under which it is stored might have an influence on the rate of this
change. The plan as outlined therefore was to obtain material
representing all of the leading commercial brands on the market and
all of the principal types of commercial containers. Two original
containers of calcium arsenate from six of the largest manufacturers
of this material were stored in a frame warehouse at the Delta Lab-
oratory of the Bureau of Entomology at Tallulah, La. One con-
tainer of each of these six brands was put in storage intact and dis-
turbed only at stated intervals when samples for analysis were drawn.
The material in the other six packages was subdivided, 25-pound
portions in each case being put into various standard types of con-
tainers and the remaining material, from 50 to 100 pounds, retained
in the original container. Four other samples, three of which repre-
sented brands included in the six just mentioned, were placed in
storage in the building occupied by the Insecticide and Fungicide
Board (220 Thirteenth Street SW, Washington, D.C.). These were
not subdivided. Samples were drawn at intervals from all of these
containers for analysis.®

The following scheme of marking for the identification of the vari-
ous brands of calcium arsenate, the place of storage, and the kind
of container, was adopted: Brands or manufacturers, A, B, C, F, H,
I, and J; material stored in Washington, W, immediately after the
letter designating the manufacturer; material stored in Tallulah, in
original containers and without subdivision, 7; sets that were sub-
divided and used for the container tests, S. All subdivisions were
stored at Tallulah.

COMPOSITION OF ORIGINAL SAMPLES.

The results of the analyses of the samples made at the time of
collection are given in Table 1.

6 In sampling the material was disturbed as little as possible. Several cores were taken by means ofa
trier, about 1} inches in diameter, at various places and extending at different angles from the top of the
package to the bottom. The head of the container was immediately replaced, or the holes through which
the trier was inserted were tightly closed.

4 BULLETIN 1115, U. S. DEPARTMENT OF AGRICULTURE. ~-

TABLE 1.—Composition of calcium arsenates at the beginning of the period of storage.

Oxids F Water-
F | ‘ Anti- | Acid-
TR tea cr acne: Lead Copper aa monic | insol- | Losson Carbon|Soluble
ple.| (As> | oxid | oxid oxid | oxid | sium. | OxXid | uble | igni- |Total.| dioxid aA
Os). | (CaO). |(Mgo). | (PPO). | (Ca0)-| inum any rc BL CO2). 1 (As
(R203). i O;).

Per ct. | Per ct. | Per ct. | Per ct. | Per ct. | Per ct. | Per ct. | Per ct. | Per ct. | Per ct.| Per ct. | Per ct.
40.55 | 43.16 A621 Trace.|¢.2"-<"- | 0.44 0. 02 0.45 | 10.88 | 97.32 Zor 0. 02

AS..| 40.18 | 39.76 1.88 (0% (35 El eee ee | 2.51 05 -44 | 10.24 | 95.97 2.78 08
AW.| 42.95 | 42.76 Te4 TACO. Ieee ook . 40 SO . 16 8.96 | 96.71 1.78 . 08
Bea all2s) 4057 bee | Praeces | oo ee s. . 66 . 16 -23 | 13.90 | 97.98 3. 62 . 20
BS..| 40.81 | 38.96 1.78 0. 70 0.70 2.10 19 ot LN 40r | O72 28 5. 30 35
BW.| 40.58 | 39.89 QOS eCRAC OR te wooee 1.12 21 -62 | 11.85 | 96.35 3. 44 69
GP) 739/35 1**36292 sy + ac: be il Pape oa 52 53 24 8.85 | 96.11 3. 30 83
CS -.| 41.59 | 43.06 .38 La fa SMe 2 8 38 50 44 8.99 | 96.11 4.47 a5
FT .| 44.10] 43.80 . 48 08 Ta RS eee 1.42 .14 . 62 4.88 | 96.07 1.40 - 00
FS..| 45.07 | 42.87 ~32 a aleeet ys 4 41.41 el ~45 5.05 |-96.15 1,91 - 03
HT.| 41.58] 41.04 - 82 ik 0) (Sic RE 2.22 a Wt 1.08 6.72 | 94.29 ig3s .10
HS .| 42.37] 42.05 1.33 PA: | es ae Ved 4 emt 1.00 6.33 | 95. 43 1.07 -10
HW} 43.10] 40.35 3.37 5740) ea 2.08 . 07 1.09 6. 86 | 97. 20 -91 at!
IT...| 40.91 | 43.16 alo ya Eee Oe |, 1350 . 08 Stl 8.05 | 96. 52 5. 95 - 08
IS...| 44.40] 43.16 soo LBS feats Sis . 86 .19 onie 6.08 | 96.7 5. 69 .39
JW .| 45.65 | 40.55 1.18 | BOs pe ney - 92 .29 .32 5.37 | 94.60 | 2.69 .30
| ] } | }

It will be noted that the arsenic oxid content exceeds 40 per cent
in every case, except that of the sample containing lead, and that
the calcium oxid and arsenic oxid values are approximately equal.
This is as it should be in a properly made calcium arsenate to be used
for insecticidal purposes. The impurities are low in all cases except
one, sample ('T, which contains more than 9 per cent of lead expressed
as the oxid. This is probably present in the form of lead arsenate
as a result of carelessness in manufacture. The presence of small
quantities of lead in the other samples is doubtless caused by the use
in their manufacture of apparatus that had previously been employed
in making lead arsenate. The copper in sample BS apparently owed
its origin to the presence of Bordeaux mixture, as small pieces of a
blue material resembling this product were visible. The water-
soluble arsenic oxid figures are reasonably low in all cases except

two, one of which is the sample containing an appreciable quantity
of lead.

CARBON DIOXID AND WATER-SOLUBLE ARSENIC OXID IN STORED SAMPLES.

The chemical criterion employed in the estimation of deterioration
in calcium arsenate is the change in the so-called water-soluble arsenic
oxid. All of the work quoted from the literature showed that con-
tact with carbon dioxid in the presence of water may greatly increase
the content of soluble arsenic oxid. The authors’ experience accords
with this. When carbon dioxid is bubbled through an aqueous sus-
pension of commercial calcium arsenate for a sufficient length of time,
the quantity of arsenic oxid rendered soluble is approximately the
same as that obtained when dicalcium arsenate is treated with
water alone, in the same concentration. Further, calcium carbonate,
under ordinary conditions, neutralizes arsenic acid only to the dical-
cium arsenate stage, showing that a basic mixture tends to revert, by

a Re
— - .

CHEMICAL CHANGES IN CALCIUM ARSENATE. y

the absorption of carbon dioxid, to a mixture of calcium carbonate
and dicalcium arsenate. It appeared that any increase in water-
soluble arsenic oxid in commercial calcium arsenate during storage,

_ therefore, would probably be the result of absorption of carbon

dioxid from the air.

Accordingly, the authors decided to determine both carbon dioxid
and water-soluble arsenic oxid in all of the samples and subdivisions
at successive intervals. Soluble arsenic oxid was determined by the
official method of the Association of Official Agricultural Chemists
and carbon dioxid in a specially designed apparatus similar to that
described by W. H. Chapin.” This method did not give extremely
accurate results but it is very rapid and sufficiently accurate for this

work. Duplicate determinations seldom differed by more than 0.10

per cent. The fact that the results here vary more than this from
the curves drawn may be explained on the basis of uneven distribu-
tion of the material in the barrels and the method of sampling. The
subsamples were always thoroughly mixed, but they were taken from
the barrels by means of a trier, and, since carbon dioxid must work
its way through from the outside of the package, it is reasonable to
suppose that three or four trierfulls might not always remove a
strictly representative sample. Taken as a whole, however, the
results leave no doubt of the fact that carbon dioxid is absorbed
under certain conditions.

The results of these examinations are reported in Table 2 and are
also shown graphically in Figures 1 to 46. The results on all the
samples obtained from one manufacturer are presented before those
of another are shown. Within each of these groups the order is as
follows: Unsubdivided sample kept at Washington; unsubdivided
sample kept at Tallulah; portion of subdivided sample kept at Tal-
lulah in original container; subdivided samples at Tallulah repre-
senting the different container tests. The last subdivisions are indi-
cated by figures following the letter designation as follows: 1, sheet-
iron drum; 2, unlined sugar barrel; 3, paper-lined sugar barrel; 4,
heavy hardwood barrel; 5, unlined veneer drum; 6, paper-lined
veneer drum.

In every graph the arsenic oxid values are represented by a solid
line and the carbon dioxid values by a broken line. The curves
are drawn in what seemed to be the most probable positions without
attempting to calculate them. In order to bring out more clearly
the relationship between their variations, the ordinate scale of arsenic
oxid (As,O,) values has been magnified to five times that of the car-
bon dioxid (CO,) values. The horizontal spaces on all the plots
indicate intervals of three months, the initial ordinate representing
in each case December 1, 1919.

7J. Ind. Eng. Chem., 10 (1918): 527.

-4| Water-| Car-
Period
' Sample ex- Date of at i
} amined. sampled. | stor- |"(V; ond
Ne age ae
i f (As2035).| (CO2).
Ht
i AW (100 pounds
i in hardwood 1920. Mos. | Perct. | Per ct.
barrel). S72 Js) 0) eel |7-4| Marae hee 0.08 1.78
June 23 2.4 07 1.88
1921.
Jan. 14 9.1 07 1.90
July 20} 15.3 -10 1.84
Nov. 25 19.4 -08 1.92
1922.
Mar. 1] 22.6 DS.) beers:
AT (200 pounds
in hardwood 1919.
barrol). 2. v2 53), Dee... le soe oe -02 2.38
1920.
Jan. 8 1S 05 2.35
Feb. 6 2-2 -05 2.36
Mar. 6 So2 02 2.41
o 0) PP 4.2 - 03 2.41
May 4 spall -05 2.46
June 10 6.3 04 2.70
July 14 7.4 -05 2.84
Aug. 14 8.4 -05 2.99
Sept. 17 9.5 05 2.55
Oct 10.5 - 06 2.58
Nov. 17 TISS 05 3.18
Dees 15 12.5 - 06 3.28
1921.
Jane" bh 1s Bes, -05 3.52
Apr. 2| 16.0 - 04 3.11
July 1] 19.0 .08 | 4.12
Oetnr 22.0 apliz. 4.88
1922.
Name? 2 2570 -10 Bb)
AS (50 poundsin
hardwood bar-| 1920.
Fel) Meeeiate Jo: Anh 20+] s es226 -08 2.78
June 10 aL aay -02 PANS"
July 14 2.8 03 2. te
Aug. 14 3.8 - 02 2.64
Sept. 17 4.9 04 2.65
Oct. 15 5.8 - 02 2s ber
- Nov. 17 6.9 -02 2.64
Dec. 15 7.8 -05 3. 26
1921.
Jan. 15 8.8 05 3.13
Apr. 2| 11.4 .06 | 3.42
July 1) 14:3 09 4.64
Octe tallies 07 4.53
1922.
Jan. 24 2024 “5 5.30
AS-1(25 pounds | 1920.
in metal drum) | Apr. 20 |.....-. -07 2.92
June 10 1a -03 2.85
July 14 2.8 03 2.50
Aug. 14| 3.8 S02 sl Di a7.
Sept. 17 4.9 02 2.46
Oct. 15 5.8 02 2.62
Nov. 17 6.9 02 2°53
Dee. 15 7.8 -04 2.76
1921.
Jan. 15 8.8 -05 2.83
Apri, 2.,| .411.4 -05 2.78
July 1] 14.3 -05 2.60
Oct: Agl 17.3 | .05 Dede
1922.
Jan; « 2 20.4 - 04 2.58

Sample ex-
amined.

AS-2 (25 pounds
inunlined su-
gar barrel)... ...

AS-3 (25 pounds
in paper-lined
sugar barrel)...

AS-4 (25 pounds
in hardwood
parrely.s.% 2.2,

AS-5 (25 pounds
in unlined ve-
neer drum)....

BULLETIN 1115, U. S. DEPARTMENT OF AGRICULTURE.

TABLE 2.—L fect of storage on chemical composition of calevum arsenate.

Date

sampled.

Period

stor-
age.

Water-
soluble

Car-
bon

Tae a a wows
Boor woos

Sots RS

Cr Dm WORD
~I wnwowd

AABN
bm
edocs

Sb
i)
>

PPS Sue we oo bo
a ee

“ae edie atte led
NOROHH WO
CARDRONE

CHEMICAL CHANGES IN CALCIUM ARSENATE.

_
>

Fig. 4.—AS-1 (25 poundsin metal drum).

ete

BULLETIN 1115, U. S. DEPARTMENT OF AGRICULTURE.

.
f°)

| Nile
ee a

Fic. 8.—AS-5 (25 pounds in unlined veneer drum).

Sample ex- Das

amined

_ AS-6 (25 pounds
_ in paper-lined; 1920.
veneer drum)... ae 20

BW (100 pounds
_ in paper-lined| 1920.
sugar barrel)... a 12

y 1922.
' Mar. 1

BT (100 pounds
in hardwood) 1919.
1) Dec.

_ BS (50 pounds in
paper - lined 1920.
sugar barrel)...; Apr. 20

sampled.

Sample ex-
amined.

CHEMICAL CHANGES IN CALCIUM ARSENATE.

9

Y TABLE 2.—Effect of storage on chemical composition of caletum arsenate—Continued.

|

Water-
Period | soluble
of | arsenic
stor- | oxid
age. |(As2Os)
Mos. | Per ct.
a ssadurs 0. 05
LW . 03
2S . 04
3.8 . 05
4.9 . 02
5.8 . 02
6.9 a
7.8 . 06
8.8 -08
cB ee f - 05
14.3 Pa
TiS 333
20. 4 Be 3:
os ee | . 69
2. 4 . 46
9.1 . 82
15.3 my A!
19,4 tt
22.6 1,09
eer - 20
ey ae4!
232 . 22
3.2 4 |
4.2 . 30
5. -16
6.3 .19
7.4 18
8.4 Bid
9.5 ai by
10.5 Sy G2
11.5 a
ieee AP 7 |
13.5 7 |
16.0 - 20
19.0 .28
22. 0 So
25. 0 ror
a Soo
Sys es
28 . 28
3. 8 . 26
4.9 40
5. 8 2B.
6.9 sao
7.8 .47
8.8 48
11, 4 Sey
14.3 . 62
17.3 aya!
20. 4 . 76

ee Ee

eeNewpyys
SRSSBGRSS

Gt Eye Go
BSS8

o
or
10°0)

OOD AAT

YP He 29 G9 ye G0 G9 G9 GO G0 G9
[SS )

PP OVO OY Ye
SRERSKES

PAD on
ADOowo
SSeS

s

BS-1 (25

in meta

BS-2 (25

Pathe

ounds

in unlined
sugar barrel)...

BS-3 (25

pounds

in paper-lined
sugar barrel)...

BS-4 (25

pounds

in hardwood

Water-
Period | soluble
of jarsenic
stor- | oxi
age. |(As20;)
| Mos. | Per ct.
flats tetee 0. 35
5 avi ~ 24
2.8 . 20
3.8 Bis
4.9 . 24
5.8 - 20
6.9 S97.
75 . 20
8.8 521
11.4 225
14.3 218
17.3 .19
20. 4 ev,
a Pian | . 30
7 acy:
2.8 soo
3.8 AGS:
4.9 67
5. 8 . 69
6.9 .79
7.8 .74
8.8 i |
11.4 - 82
14.3 . 76
WAR) 78
20. 4 - 87
pe aoe 8B 7.
1 ae - 46
2.8 . 60
3.8 . 62
4.9 By 5°
5. 8 Se pe
6.9 Le
7.8 74
8.8 bt if |
11.4 .76
14.3 .76
a a - 76
20. 4 85
See . 29
17 BD7;
2.8 2D
3.8 e25
4.9 325
5.8 toe
6.9 . 30
7.8 .29
8.8 aoe
11.4 . 30
14.3 .30
ay OG: .59
20. 4 . 68

Pee eee oS
efteseeaes

aaa
SReS

la
BA

NP MAA QE

NPAAA MBO
ek: heorker) Oe
yan aie aes

eine
SRG

3

sat A sll sell scale sell sd
OD bm 2 SI 910100
SSEBOSoS

Porarer
BAER

>
or
—

BULLETIN 1115, U. S. DEPARTMENT OF AGRICULTURE.

10

SLA CLIV7

YOY W
SEN Sig SN 280

CSseRggr?
LVZIO FS

Fig. 9.—AS-6 (25 pounds in paper-lined veneer drum).

PER CENT
EVV VIIYo

Fig. 10.—BW (100 pounds in paper-lined sugar barrel).

Fia. 11.—BT (100 poundsin hardwood barrel).

PLP? CENT

® ©
ENV VIISTYo

Fic. 12.—BS (50 pounds in paper-lined sugar barrel),

CHEMICAL CHANGES IN CALCIUM ARSENATE. hy *

a Po ‘
eter es
eos CE HE A CL 9
20 as-g tence set 26t
2.0 We eed 04‘
x 1.0 0.2

O O
Fig¢, 15.—BS-3 (25 poundsin paper-lined sugar barrel).

cE A A
hso| | sree oe Lede | tl 8
9 GIR am Sl a A
v2 068
NE 04-
Vso a2"

Fia. 16.—BS-4 (25 pounds in hardwood barrel).

| 12 BULLETIN 1115, U. S. DEPARTMENT OF AGRICULTURE.

TABLE 2.—Effect of storage on chemical composition of calcium arsenate—Continued.

Perioa | Water-| Car- _ _| Water-| Car-
} Sample ex- Date -| . of splubie pon Sample ex- Date: Eeriod solope au
} amined. sampled. | stor- =, Bxid amined. sampled. stor: | oxid | 4nd
if a8e- |(As20s5).| (CO2). age. |(As:0s).| (CO:).
BS-5 (25 pounds CS (50 pounds
in unlined 1920. Mos. | Perct. | Perct. in paper-lined | 1920. Mos. | Per ct. | Per ct
veneer drum)-..} Apr. 20 |....... 0. 29 4. 80 veneer drum) | Sept. 17 4.9 0.36 4.89
June 10; 1.7 -35 | 5.15 (continued.) | Oct. 15| 5.8 .35 | 5.47
July 14 2.8 30 5. 08 Nov. 17 6.9 40 5. 78
Aug. 14] 3.8 36| 5.68 Dec. 15| 7.8 38 | 5.61
Sept. 17 4.9 50 5. 80
Oct. 15 5.8 48 5. 88 1921
Nov. 17 6.9 Cl (es See Jan. 15 8.8 41 5.78
Dee. 15 7.8 67 6. 63 Apr. 2) 11.4 64 4.04
July 1 14.3 -41 6.18
' 1921 Octs oot 17.3 -45 5.90
Jan. 15 8.8 - 64 6. 84
Arr.” 2)| 11.4 s74.1) -7.at 1922.
July 1 14.3 Sh 7.23 Jan. 2] 20.4 54 6. 22
Oct. - 1 17.3 - 76 6.97
CS-1 (25 pounds 1920.
1922. in metaldrum)| Apr. 20 |....... 15 4.68
Jan. 2] 20.4 . 94 7.07 June 10 1 er .14 4.33
ay 14 a 14 4.22
cs ug. 14 ; 14] 4.63
BS-6 (25 pounds Sept.17| 49| 217] 4.37
in paper-lined | , 1920. Oct. 151| 5.8 || « aaeear
veneer drum)..| Apr. 20 |.-..... .34 4.79 Nov. 17 6.9 12 4.47
June 10 Tad 74 | 4.74 Dea 15 73 12 4.10
July 14] 2.8] .28| 4.83 ; ;
Aug. 14 3.8 25 5. 28 1921
Sept.17| 4.9 42) 5.10 Jan. 15| 88] .13|- 4.60
Oct. 15 5.8 32 5.11 ‘Apr. 2 11.4 “14 4.99
Nov. 17 | 6.9 39 |-.-.--- July 1] 143] 214] 4.59
Dec. 15] 7.8 43) 5.93 Oct. 1| 17.3] ..14| 4:38
1921 1922
Jan. 15 8.8 255 6. 23
Apr. 2| 11.4 -60 6.68 Jan. 2]. 20.4 12 4,20
ar barrel)..... prs 20 Pile :
1922. r E ) June 10| 1.7] :20| 4.88
Jan. 2) 20.4) .94] 6.99 July 14] 2.8] .27| . 5.31
7 aoe is] 8) oe
CT (100 pounds ept. 1 : ; 2
mere | dee] eo 2] $3) cal BB
es ec. eer eeee ° . . . . .
ba ) Dec. 15 7.8 47 6.00
1920. ,
Jan. 8 i . 76 3.29 1921 Q
Feb. 6 Pe .65 3.33 Jan. 15 8.8 -45 6.30
Mar. 6 Sek - 06 3.45 5 0) eee i Pt le .42 6.17
Apr. 7 4.2 44 3.52 July 1 14.3 44 6. 25
May 4 Bak 52 3.60 Oct. 1 li .42 6.00
June 10 6.3 54 3.74
July 14 Tt: . 60 3.79 1922.
Aug. 14 8.4 . 69 3.90 Jan. 2| 20.4 54 6.20
Sept. 17 9.5 -47 3.43
Oct. 15] 10.5 .52| 3.63 |} CS-3 (25 pounds
Nov. 17} 11.5 .69 3. 87 in paper-lined 1920.
Dec. 15 | 12.5 . 63 4.19 sugar barrel)..| Apr. 20 |....... 15 4.40
June 10 5 iy -16 4.47
1921. July 14] 2.8 <7 | 24566
Jan. 15 a, - 55 3.93 Aug. 14 3.8 -38 OST
Apr. 2 16.0 43 5.97 Sept. 17 4.9 - 50 5.98
July 1 19.0 -62 3.98 Oct. 15 5.8 -45 5.76
Oct. 1] 22.0 Rift 4.17 Nov. 17 6.9 . 46 6.06
Dee. 15 7.8 43 6.14
al 25.0 70| 4.40 1921
oe Jan. 5 ii “— ce
CS (50 poundsin Apr. 1. , ,
pateeiioee ve- 1920. July 1] 14.3 -44 6.31
neer drum)....} Apr. 20 |....... 15 4.47 Oct. el Miss -44 6.31
july 14 28 a 176 1922
Ju 1 ; : . 5
Aue 14] 3.8 .24 | 5.24 Jan, 2| 20.4 52| 6.26

13.

-. GHEMICAL CHANGES IN CALCIUM ARSENATE.

LNID WTS

lia. 18.—BS-6 (25 pounds in paper-lined veneer drum),

Fig. 19.—CT (100 poundsin paper-lined veneer drum).

Fig. 20.—CS (50 pounds in paper-lined veneer drum).

14 BULLETIN 1115, U. S. DEPARTMENT OF AGRICULTURE.

ZO ee
wage
Reseed a AN PO ed gE EEN
r SS ae ee oe
vee ee ee ee ah
Bet Tiel ales ois
ye me
eA oa LN ‘
(Sige
ysl emis
Lif ere
reas
aera cain
i
canes:

ZO 14
‘ 1 dell at 12 >
< yo wo Q-
W 40 QBs
& 40 06 N
‘ 20 04

Fia@. 24.—CS-4 (25 pounds in hardwood barrel).

CHEMICAL CHANGES IN CALCIUM ARSENATE. 15

Taste 2.—Effect of storage on chemical composition of calcium arsenate—Continued.

Period Water-| Car- Period Water-| Car-

luble| bon ¢ soluble} bo
Sample ex- Date an tet Sample ex- Date of ; =
amined sampled. | stor- |"™i4" oxid amined. sampled. | stor- | 73° ea
a8e- |(As20s).| (CO2). || A5°- | Ase0s).| (CO2).
CS—4 (25 pounds FS (75 pounds
in hardwood 1920. Mos. | Perct. | Perct. in paper-lined 1920. Mos. | Per ct. | Per ct.
barrel)-—<. -’.. - Aprsa (. 2. 0.14 4.54 veneer drum)..} Apr. 20 |..-.... 0. 04 1.91
June 10 LY -19 4.45 June 10 5 by . 08 1. 85
July 14 2.8 .15 4.37 July 14 Re .06 2, 94
Aug. 14} 3.8 18 | 4.84 Aug. 14| 3.8 .07 | 3.62
Sept.17] 4.9 -20} 4.57 Sept.17| 4.9 .07 | 2.75
Oct. 15; 5.8 22 4.92 Oct. 15] 5.8 .05 | 3:36
Nov. 17| 6.9 -25 {5.33 Nov. 17| 6.9 -10| 4.81
Dee. 15| 7.8 -27 | 5.36 Dec. 15] 7.8 .07] 4.30
iI
1921. " ripest 1921.
Jan. 15; 8.8 -25 5.32 | Jan. 15| 8&8 -10] 4.19
Apr. 2] 11.4 -40 5.15 Apr. 2] 11.4 att 4,6
July 1; 14.3 -42) 6.09 July 1| 143 .22| 5.54
Oct. 1] 17.3 747 | 6.14 | Oct. Ul te3 "96 | 5,98
}
1922, 1922
Jan. 2{| 20.4 54 6.08 | Jan. _2| 20.4 36 5.75
CS-5 (25 pounds | FS-1 (25 pounds 1920.
in en ve- 1920. || in metaldrum)| Apr. 20 |..-.--- . 05 2. 09
neer drum)....| Apr. 20 |....... 17} 4,91 | June 10} 1.7 .@5;)', 1.72
June 10} 1.7 16] 4.51 July 14} 2.8 -03 | 1.64
July 14 2.8 20 4,54 Aug. 14 3. 8 05 1.74
Aug. 14/ 3.8 217) 4.94 Sept.17; 49 -05 | 1.67
Sept. 17 4,9 134 5. 40 Oct. 15 5.8 . 05 1, 88
Oct. 15 5.8 be, 5.67. Nov. 17 6.9 . 05 1.70
Nov. 17| 6.9 45] 5.72 Dec. 15| 7.8 -05 | 2.16
Dec. 15| 7.8 46} 6,28-
1921.
1921. Jan. 15 8.8 205 1.79
| Jan. 15 ars .46 6. 36 | Apr. °2] 11.4 . 03 1.98
- Apr. 2] 11.4 46} 6.06 July 1) 14.3 .05 | 2.36
July 1] 143 .45 6. 24 Oct... 1} 17.3 . 05 1.81
Oct. 1 17.3 . 43 6. 07 .
1922.
} 1922 Jan. 2{| 20.4 05 1. 88
Jan. “2'} 20.4 Soe 6.91 |
CS-6 (25 pounds | FS-3 (25 pounds
in paper-lined | 1920. || in paper-lined | 1920.
veneer drum)..| Apr. 20 |_...... 15 4.39|| Sugar barrel)...| Apr. 20 |-.-...- - 06 2.01
June 10} 1.7] .16| 4.24 June 10) 17] .08} 2.30
July 14] 28 16 |. 4.24 | July 14] 2.8 .05 | 3.12
Aug. 14 3.8 wlZ 4.62 Aug. 14 3.8 .07 3. 49
Sept. 17 4.9 . 20 4.39 Sept. 17 4.9 - 09 3. 81
Oct. 15 5.8 sain 4, 56 Oct. 15 5.8 - 10 4.53
Nov. 17 6.9 . 24 5. 06 Nov. 17 6.9 15 5. 32
Dec. 15 7.3 . 20 5. 44 Dee. .15 7.8 a 5. 62
1921. 1921.
Jan. 15 8.8 -25 5: oO Jan. 15 8.8 -25 5. 70
Apr. 2) 11.4 .20} 5.29 Apr. 2| 11.4 .382| 5.61,
July 1] 143 .39 | 5.59 July 1| 143 -34] 5.74
Oct. 1 17.3 . 48 5591 Ochi t I 7-3 ~ a2 5. 68
1922 1922
Jan. 2] 20.4 54 5. 83 Jan. 2] 20.4 41 5. 62
FT (100 pounds
in unlined ve- 1920. FS-4 (25 pounds
‘ neer drum)....)| Apr. 7 |..-...-. 00 1.40 in hardwood 1920.
, May 4 9 -O1 1,44 barrel)... <cscab Apt. 20-}<5-2-- 05 2. 05
June 10 2.1 . 03 1. 62 June 10 i Bye 05 1. 87
July 14 3.2 . 03 1.65 July 14 2.8 -05 1. 88
Aug. 14 4, 2 | . 03 1. 66 Aug. 14 3.8 -07 2. 00
Sept.17| 5.3] .02] 1.83 Sept.17| 4.9 -06| 2.05
Oct. 15 6.3 | - 02 1. 94 Oct. 15 5.8 - 05 2.04
Noy. 17 7.3.4 . 02 2. 7> Nov. 17 6.9 - 08 2. 06
Dec. 15 8.3 . 02 2. 38 Dec. 15 7.8 -05 2. 94
3 Z 1921. 1921.
Jan. 15 9.3 . 02 2.41 Jan. 15 8.8 . 06 2. 71
Ape 27 1 Peo 2. 42 Apr. 2] 11.4 09 2. 38
July 1| 147) .05 3. 97 July 1] 143 .05 2. 72
Odt..—-1-}.-.17.8.)...04 3. 78 Oct. 1} 17.3 07 3. 04
1922. 1922.
4 Jan. 2! 20.8: #09 3.09 Jan. 2) 20.4 .07 3. 38

16

BULLETIN 1115, U. S. DEPARTMENT OF AGRICULTURE.

_ _Fiq@. 28.—FS (75 pounds in paper-lined veneer drum).

CHEMICAL CHANGES IN CALCIUM ARSENATE,

SS eae

embaarrine | han’ | ee nomen Ire ade

SO O_o Lo”. 4 O
e

>

Fig. 31.—FS-4 (25 pounds in hardwood barrel).

Fic. 32.—FS-5 (25 pounds in unlined veneer drum),

~

18 BULLETIN 1115,°U. S. DEPARTMENT OF AGRICULTURE.

TasLe 2.—EH fect of storage on chemical composition of calcium arsenate—Continued.

: Water-} Car- ; : Water-| Car-
Period Period
Sample ex- Date pada ae Sample ex- Date of sclubja “ag
amined. sampled.| stor- |" Oyiq id amined. sampled.| stor- |*O4° | oxid
} age xi oxi age. oxi oxi
; (As205).] (CO2). (As2O5).} (COs).
FS-5 (25 pounds HS (100 pounds
in unlined ve- 1920. Mos. | Per ct. | Per ct. in hardwood 1920. | Per ct.| Per ct.| Per.ct.
neen.drum)_24.\') Apr. 120 |b... 22: 0.05 1.90 Darrel) 2. eee. ADTs 20 ste ssoas 0.10 1.07
June 10 i bf - 06 1.96 June 10 lod 05 95
July 14 2.8 05 1.88 July 14 2.8 . 04 - 88
Aug. 14 3.8 - 05 2. 26 Aug. 14/, 3.8 02 - 98
Sept.17| 49 S064)" | 2.53 Sept. 17| 4.9 02 85
Oct....15 5.8 05 2. 68 Octe15 5. 8 02 1. 02
Nov. 17 ~ 6.9 -07 2.95 Nov. 17 6.9 02 1. 04
Dec. 15 7.8 -06 2. 98 Dec. 15 7.8 04 1, 28
1921. | 1921. |
\ Jan. - 15-{-—&8 -06} 3.28 Jan. 15; 88 02 94
Apr. 2 1:4 .05| 3.08 Apr. 2} 11.4 02; 1.48
July 1] 143 .08}| 4.36 July 1) 143 02) 1.54
Ocal 1773 09 4,77 Oct. - 1 17.3 02 i seas!
1922 1922
Jan. 21} 20.4 22 5. 38 Jan. 2] 20.4 07 1. 69
HS-1 Oo opuea) peau ; Se
; in meta pre ZOMEo fe ce. me! 6
$ FS-6 (25 pounds June 10] 1.7| .04) 1.00
+ in paper-lined | 1920. July 14] 2.8 . 04 9
veneer drum)..| Apr. 20 |....... 06 1.93 Aug. 14 3.8 02 .92
June 10 7 05 2.16 Sept. 17 4,9 02 .93
July 14} 2.8 -05} 2.34 Oct. 15] 5.8 02 95
Aug. 14| 3.8 +05] 2.35 Nov. 17| 6.9 02, 1.22
Sept.17; 4.9 -06] 2.30 Dee. 15] 7.8 62;)', | 1.18
Oct. -15 5.8 +05 2. 62 |
Nov. 17 6.9 “07 3. 48 1921
Dee. 15 7.8 07 3. 79 Jan. 15 8.8 02 .98
Apr..o2t| 11.4 02 -97
1921 July 1] 143 02 93
Jan. 15 8.8 -07 4.06 Och" 173 .02 1.01
Apr. 2} Lid -08 3. 80
July 1 14.3 12 517 1922
, Oet.-—1-+|-123 33 5. 51 Jan.+ 2} 20.4 -05 1.02
1922. HS-4 ape ee
Jan. ~~ 2°} 2004 39 5. 23 in hardwood 1920.
armel) esosecees | OA DEp COE es see alk 1.08
we WH Lv pe 1.06
HW (50 pounds uly 1 ° p08 | ae EL
in hardaroad 1920. ee ee ee oh Jee
Sept.17| 4.9 02°} 4/07
Darrel): 2..}: 1 oS PN A | SASS yl! - 87 Oct. 15 5,8 02 1.06
June 23 2.4 08 . 90 sik mt F ;
Nov. 17 6.9 . 02 1.52
1921. Dec. 15 7.8 02 1. 66
ee pea 104
wy : e ° Jan. :15 || 88 |) -s0m|> tad
NOYa. BP of onde OF sh} « Apr. 2| 11.4 02| 1.38
1922 July 1 14.3 02 2. 52
=| Mar a: 1 22.6 5 Oct. 1 iby a} 02 1.88
1922.
Jan. 2| 20.4 0% 1.81
HT (100 pounds
in hardwood 1920. HS-6 (25 pounds
barrel)®.2 2. 4Apr. 20s... -10 1.33 in paper-lined 1920.
ay 4 5 -07 - 84 veneer drum)..}| Apr. 20 |......- old 1.05
June 10 i bee . 06 86 June 10 17 - 05 1.02
July 14 2.8 . 04 97 July 14 2.8 . 07 1.15
Aug. 14 3.8 . 02 99 Aug. 14 3.8 . 05 1.10
Sept. 17 4.9 - 02 91 Sept. 17 4.9 . 02 1, 22
Oct. 15 5. 8 .02 1.25 Oct. 15 5.8 . 05 1, 28
Nov. 17 6.9 - 02 1. 52 Nov. 17 6.9 . 02 1. 48
Dee. 15 7.8 . 02 2.35 Dec. 15 7.8 . 02 2. 24
1921 1921 .
Jan. 15 8.8 . 02 4 Jan. 15 8.8 . 02 1. 87
Apr. 2°) sie4 . 02 2. 92 ADT. Zeal TA - O2|\- 1°78
July 1 14.3 -05 2. 87 Jul 1.04.3 . 04 2. 56
Oct. ll edliZs . 04 2.40 Oct.) 27.3 - 05 3.09
1922 1922
Jan. 2! 20,4 ah2 3. 72 Jan, 2! 20,4 $07 <3 abe

CHEMICAL CHANGES IN CALCIUM ARSENATE.

oe aes pled Re

Fig, 36.—HS (100 pounds in hardwood barrel).

ques © oe a O a Oso coe ( eos aoe © comes coo C) commen come ©) quences eemen

19:

20 BULLETIN 1115, U. S. DEPARTMENT OF AGRICULTURE.

14

h2
AY}

a,

ag Serene oa ee Re

ona

dn amore “aa

Fig. 40.—IT (100 pounds in paper-lined sugar barrel).

CHEMICAL CHANGES IN CALCIUM ARSENATE. St

TABLE 2.—Effect of storage on chemical composition of calcium arsenate—Continued.

{
|

- 4| Water-| Car- | | ersaq| Water-| Car-

Period Period |
Sampleex- | Date of cca ete Sample ex- Date ae ae
amined. sampled.| stor- |" oxid | oxid amined. sampled.| stor- |*osa'"| oxid

IT (100 pounds | | '| IS-3 (25 pounds in
in paper-lined | 1920. Mos.| Per ct.| Perct. || paper-linedsug-| 1920. is Per ct.| Per ct.
sugar barrel)..-| Apr. 20 |....... 0. 08 5.95 || arbarrel)(con.).| Sept. 17 4.9 0. 93 6. 59
ay 4] 0.5 .07| 5.61 | Oct. 15] 5.8] 93 | 6.20
June 10} 1.7 .06 | 5.92 Nov.17| 6.9] .92| 6.37
July 14} 2.8 07 | 6.25 | Dec. 15} 7.8 | 96 | 6.61
Aug. 14 3.8 . 07 5. 85 1921. |
Sept. 17 4.9 . 06 6. 08 Jan. 15} 8.8; .91 6. 64
Oct. 15] 5.8 .05| 5.94 Apr. 2] 11.4 .88 | 6.46
Nov. 17 6.9 12 6. 76 July 1 14.3 . 90 6.41
Dec. 15 7.8 12 6. 69 07 ae | OE 7 « 94 6. 40
1921 1922.
Jan. 15| &8| .28] 6.90 Jan. 2| 20.4 94| 7.10
Apr. 2] 1.4 18 6. 60 Q .
July 1| 143] .65| 7.4 ee id sealer is |
Oct. "I ] 17-3 42) 7.18 On | 9
1922 ; 2 barrel) o- 2% - . J ADEs “ aes oe ae
; - -p aie une : 32 512
pan. 2} 24 | ___f 44. July 14/28} 232] 5.90
IS (100 pounds | Aug. 14 3.8 39 5. 83
in paper-lined 1920. Sept.17| 4.9 51 5. 65
sugar barrel)... 7 oe. ee .39 5. 69 Oct. AS 5.8 49 5. 71
| June 10 47 .38 6.12 Nov. 17| 6.9 Ar) 6. 00
July 14} 2.8 237 5. 70 Dee--15.-|-— 78 71 5. 98
Aug. 14 3.8 - 50 5. 79 1921
Sept. 17 4.9 . 59 6. 23 Jan. 15} 8.8 63 6. 40
Sri ts 5.8 . 69 6. 08 Apr. ~2| 114 Rw | 6. 23
Nov. 17 6.9 .73 6.16 July” 2), v3 78 6. 27
Dec. 15 7.8 . 68 6. 39 Oct. 81 17.3 94 6. 43
1921. j922. |
Jan. 15 8.8 .79 6. 46 Jan. 2) 20.4 94 6. 30
Apr. 2} 11.4 .77| 6.49 | 2
iaiy i] ia | ia] sae | 15.6 C5 pounds)
—_ 17.3 -83} 6.42) veneer drum).. Ao = — 37 owe
. Z une 10; 1.7 : . 36
Jan. 2) 20.4 88 | 6.89 July 14| 2.8| 62] 611
IS-1 (25 pounds | 1920. Aug. 14/ 3.8] .79| 6.25
in metaldrum)} Apr. 20 |....... .36| 6.09 | Sept.17/ 4.9 .97| 6.45
June 10 CT | Be 5) 6.06 | Oct. 15 5. 8 .99 6. 30
July 14| 2.8] .32| 5.58) Nov.17| 6.9] 1.00] 6.54
Aug. 14] 3.8 36] 5.82 Dec. 15| 7.8 .96| 6.64
Sept. 17 4,9 . 43 5. 85 | 1921
Oct. 15 5. 8 son ST Jan. 15 8.8 97 6.78
Nov.17]} 6.9 «oT 5. 86 | Apr. 2] 11.4 92 6. 32
= - -
Dee. 15 7.8 40 5, 24 | July 1 14.3 . 90 6. 42
1921. | Oct=.. bl tis -99 6. 61
Jan. 15 8.8 36 6. 00 1922.
Apr. 2] 1L4| .35/ 6.01 | Jan. 2| 20.4| .97| 6.27
y 1) ; 6.11 | yw (50 pounds | 1920
aor Yj 42.3 -36 6.08 in metal drum)| Apr. 12 |....... . 30 2. be
Jan. 2] 20.4] .54] 5.78 ou en some | eae | Seog
IS-3 (25 pounds Jan. 14| 9.1| .30|] 277
in paper-lined | 1920. | July 20; 15.3 -28| 2.64
sugar barrel)...| Apr. 20 |....... -31| 5.51 || Nov. 25| 19.4 oot. aod
June 109 EY . 4 6. 09 || 1922.
July 14] 2.8 Bal ij 6. 58 Mary f 2220 1s se: lessee
Aug. 14 3.8 .92 6. 55 |

WIP SFA

7

Fig. 41.—IS (100 pounds in paper-lined sugar barrel).

22 BULLETIN 1115, U. S. DEPARTMENT OF AGRICULTURE.

Fic. 45.—IS-6 (25 pounds in paper-lined veneer drum).

CHEMICAL CHANGES IN CALCIUM ARSENATE. 23

DP HTS

NV:

Q §
S
P4

Fig. 46.—JW (50 pounds in metal drum).

DISCUSSION.

The arsenic oxid in water-soluble form and the carbon dioxid
increased in all of the samples except those packed in the tightest
containers. The close relationship between the increase in water-
soluble arsenic and in carbon dioxid is plainly shown by the paral-
lelism between the carbon dioxid and arsenic oxid curves for most
of the samples. ,

In some cases the carbon dioxid content increases from the begin-
ning, but the quantity of water-soluble arsenic oxid begins to increase
only after some time has elapsed. This is undoubtedly due to the
fact that a certain quantity of free lime is necessary to repress the
“solubility”? (really decomposition) of the calcium arsenate, and any
free lime in excess of this amount can carbonate without affecting
the soluble arsenic oxid. Once this limit is passed, however, decompo-
sition begins. Many of the curves also show a limiting value for each
of the two changes, these limits being reached at approximately the
same time. This is well shown in the case of subsamples stored in
sugar barrels, the most open containers, the greater number of
which reached equilibrium in from six to nine months. It might
naturally be assumed that this corresponds to the complete carbona-
tion of the free lime in the samples, the final mixture being essentially
tricalcium arsenate and calcium carbonate. Calculating the limit-
ing carbon dioxid values to their equivalent calcium oxid values and
subtracting these from the total calcium oxid, however, leaves calcium
oxid remaining in amounts from 0.2 to 4.8 per cent in excess of
the quantity necessary to form tricalcium arsenate with the total
arsenic oxid of the sample. Pure tricalcium arsenate octahydrate
[Ca,(AsO,),.8H,O], containing 42 per cent total arsenic oxid, gave
about 3 per cent water-soluble arsenic oxid, while the completely
carbonated commercial samples exceeded 1 per cent in only one case
(BW), which seems to argue against this being the only calcium
arsenate in commercial samples. Further work will be necessary
before the question of the presence of basic arsenates can be defi-
nitely settled.

94 BULLETIN 1115, U. S. DEPARTMENT OF AGRICULTURE.

There is a marked difference in the rate of change in the samples
attributable to the types of containers. The samples stored in the
metal drums showed practically no change. The change in those
stored in the other containers varied from a very slight one, in
the case of the tightest hardwood barrels, to a marked one in the
case of the more open containers, such as sugar barrels. For the
hardwood barrels the average increase in water-soluble arsenic oxid
after 12 months was 0.06 per cent (maximum, 0.31 per cent) and
in carbon dioxid, 0.85 per cent; at the end of 20 months, the average
increase was 0.15 per cent in soluble arsenic oxid (maximum, 0.53

per cent) and 1.40 per cent in carbon dioxid. The samples stored

in the paper-lined and unlined veneer drums showed little difference.
At the end of 12 months the average increase in soluble arsenic
oxid was 0.15 per cent (maximum, 0.55 per cent) and in carbon
dioxid 1.38 per cent. After 20 months the average increase in
soluble arsenic oxid was 0.30 per cent (maximum, 0.65 per cent)
and in carbon dioxid 2.21 per cent. In the lined and unlined sugar
barrels the average increase in soluble arsenic oxid after 12 months
was 0.31 per cent (maximum, 0.57 per cent) and in carbon dioxid
1.72 per cent. After 20 months the soluble arsenic oxid increase
averaged 0.45 per cent (maximum, 0.63 per cent) and the carbon
dioxid increase averaged 2.01 per cent.

The average results showing the behavior of the material stored in
the different containers are given in Table 3 and Figures 47, 48, 49,
and 50. Each curve represents the average of the products of dif-
ferent manufacturers contained in packages of the same type. Four
types of containers, metal drum (1), paper-lined sugar barrel (3),
hardwood barrel (4), and paper-lined veneer drum (6), are repre-
sented under the six brands* included in the subdivision tests, and
all of these (23 subdivisions) were subsampled on exactly the same
dates. Each type of container is treated separately in order to
bring out the parallelism between the carbon dioxid and water-
soluble arsenic changes, and two graphs, showing all four curves for
carbon dioxid and for arsenic oxid, respectively, are presented in
Figures 51 and 52.

8 Only five brands are represented in the case of the paper-lined barrels.

/

CHEMICAL CHANGES IN CALCIUM ARSENATE, 25

TasBLe 3.—Effect of type of container on chemical composition of calcium arsenate during

storage.
| od} selubie | Carbo Period| selnble(Carl |
Period} soluble | Carbon y eTiod| soluble |Carbon
Type ofcon- |. — ofstor-| arsenic Sypepie Peta: * ofstor-| arsenic | dioxid
tainer. ample. | age. | oxid a Sampiec-| age. | oxid |(CO2).
| (AS20s) (AS:05)|
| es | —_——_
Metal drums Hardwood bar- | |
(samples AS- rels (samples |
1, BS-1, CS-1 AS-4, BS-4, |
FS-1, HS1,| 1920 Mos. | Per et. | P CS-4, FS4, 1920 Mos. | Per ct.| Per ct.
IS-1jpe.ts 3 } Apr. 20 }....-.- 0-18 HS+4, IS-4)...| Apr. 20 }....... | 0.17| 3.54 /
| June 10 1.7 | 14 June 10 i ay 16 3. 54 |
July 14 | 28] (2B July 14 | 2.8| ..15| 3.67
Ang. 14 9-04-13 Aug. 14 378) 3.17 | 3.91
Sept.17| 49 15 Sept. 17 4.9} .22| 3.91
Oct. 15} 5.8 13 Oct. 151 5.8] .23] 4.06
| Nov. 17 6.9 | 13 | Nov.17| 69] .26] 4.37
| Dee. 15| 7.8 14 | Dee. 15| 7.8 | .29| 4.51
| 1921. | | 1921.
| Jan. 15} 8.8 14] 3.53} Jan. 15] 8&8 | .27 | 4.47
| Apr. 2] 114 .14| 3.45 Apr. 2] 11.4 31| 4.49
; July 1] 143 .13 3. 54 |) July 1] 14.3} “3 4. 86
fOd. 11 17.3} .14]~ 3.36] Oct. 1| 17.3] 142 | 5. 06
| 3922. | | | 1922 |
|} Jan. 2 20.4 16 3. 33 |) | Jan. 2 | 20.4 | 46 5. 09 :
| i} |
Paper-lined ) | Paper-lined | | |
sugar _ barrels | | | veneer s |
(samples AS- | } (samples AS |
3, BS-3,CS-3,| 1920. | 6, BS-6, CS-4, | |
S-3, IS-3)-..-] Apr. 20 j......- | - .48| 400j)| FS6, HS6,! 1920. |
| June 10 1.7 | 26} 4.41 15-8) csp ven, Apes 2h p-+- 16} 3.53
July 14] 28) .32) 477] | June 10| 1.7 .16| 3.56
Aug. 14] 3.8] 4 5.29 July 14] 2.8 | .20| 3.56
Sept. 17 | 4.9} -47 5. 50 | Aug. 14 3.8 .23 3. 74
Oct. 15| 5.8] .45 5 46 | Sept.17} 49] .28| 3.81
Nov. 17 6.9 .50} 6.09 | | Oct. 15} 5.8 .2| 3.73
Dec. 15| 7.8 -49| 6.27 | | Nov.17| 69 .29| 4.29
| Dec. 15) 7.8] .29] 4.58
1921. |
Jan. 15] 8&8 52] 6.27 1921.
Apr. 2] 11.4 -55| 6.25 |Jan. 15| 8.8 .32
July 1] 143 .55| 6.31 | Apr. 2] 11.4] 31
Oct. 1] 17.3 .55| 6.34] July 1] 14.3
r | | | Oct. 1] 17.3 |
|
| Jan. 2/ 20.4 60} 6.45 | 1922
| | Jan. 2] 20.4 52

FEA CELI 7

O
Fig. 47.—Average results with AS-1, BS-1, CS-1, FS-1, HS-1, IS-1 (metal drums).

26 BULLETIN 1115, U. S. DEPARTMENT OF AGRICULTURE.

Fic. 48.—Average results with AS-3, BS-3, CS-3, FS-3, IS-3 (paper-lined sugar barrels).

All of the sugar barrels were in bad condition at the end of the test |
because of handling incident to sampling. The results of the tests |
show the unfitness of this type of container as a package for com-
mercial purposes.

It is plainly shown that the containers are rated in the same order
by both the carbon dioxid and the water-soluble arsenic oxid results. }
The metal drums show no change and the sugar barrels show the }
most rapid change, the other two being intermediate. Little dif-
ference between the lined and unlined containers of the same type
is observed. The calcium arsenate stored in the sugar barrels }
apparently reached equilibrium in most cases in approximately |
eight months. No seasonal variation in the rate of change is
apparent.

Very little information concerning the effect of locality was ob-
tained. Strictly comparable results were possible only with samples
AW and AT, and samples HW and HT. In both cases the rate of
absorption of carbon dioxid was higher at Tallulah than at Wash-
ington. The authors are not in a position to state whether or not
this was due to a higher carbon dioxid content in the air at Tallulah
or to some other condition.

VY WA ®AAN
S 96O-9-9--S45-S

FER CLIVI™

~

Fig. 49.—Average results with AS-4, BS-4, CS-4, FS-4, HS-4, IS-4 (hardwood barrels),

CHEMICAL CHANGES IN CALCIUM ARSENATE. oF

Fie. 52.—Effect of container on water-soluble arsenic oxid.

SUMMARY.

Commercial calcium arsenate in the dry powdered form manufac-
tured for insecticidal purposes absorbs carbon dioxid slowly from
the atmosphere during storage and increases in water-soluble arsenic-
oxid content, unless it is packed in containers that are practically
air-tight. The rates of these changes show a close relationship and
depend largely upon the type of container in which the material is
packed.

The absorption of carbon dioxid is the first change noted. This
is followed a little later by a rise in the water-soluble arsenic oxid

28 BULLETIN 1115, U. S. DEPARTMENT OF AGRICULTURE.

ial “ici i

content. Carbon dioxid is taken up until all of the calcium present
in the form of the oxid or hydrate is completely carbonated, at —
which point the increase in water-soluble arsenic oxid also ceases in
most cases.

The different types of commercial contai. ers tested may be ranked
in the following order: Sheet-metal drum, in which practically no
change occurred; heavy hardwood barrel; veneer drums (both un-
lined and paper lined); sugar barrels (paper lined and unlined).

Of the calcium arsenates examined, none of those stored in sheet-
metal drums or in tight hardwood barrels, with possibly one excep-
tion, suffered sufficient change in 20 months to be injuriously affected
for use from the standpoint of plant toxicity.

In a few cases where calcium arsenate was stored in unlined and
in paper-lined veneer drums, and m unlined and in paper-lined sugar
barrels, the calcium arsenate at the end of the 20-month period
contained soluble arsenic oxid in sufficient amount to make doubt-
ful its safety for application on certain foliage.

The shght changes in the chemical composition of calcium arse-
nate under certain conditions of packing during long storage can be
practically completely avoided by the use of tight sheet-metal drums. ~

ADDITIONAL COPIES
OF THIS PUBLICATION MAY BE PROCURED FROM
THE SUPERINTENDENT OF DOCUMENTS
GOVERNMENT PRINTING OFFICE
WASHINGTON, D. C.
AT

10 CENTS PER COPY
V

|

5
-
; :
' - J r
:
1
ae i 7
= “ = 7 —
4
Lr f
¥ ow
me Ue a) ;
‘
ally = - a
a : : i
7 .
- ~
-_ i ee a
ms on oa
a A
. . vi
aa =
; 4
iT) .
'
s ¢ —_
-
- o 7 a
‘. a _ 1
(
w o) a
aD AN, Oped
a e. _

ml ;

7 .; Pa : a Engle :

. 4 pen aoe 2% 2
1 _ alk > #

Oe t, hh toe:

2 il

ie,
-
|
7
=
.
4
7
7

”*
a.
ro
-
..
i?
~_
ad
¢
y'
=

-— {ee f -_ a 7 > ane...
rf +" f a <> + ey _ We ¢ Phe 7 beet | : vi: « awl =
ea eo ree pe tog : : , 7. oe ‘
‘ > akg i A a betta! tie we =

SS a es
LP 95 ae ‘Ve Gi_e "(t -oee
_ a wt a1 a ee 7, ery ae . = mG

rae Dien aa oe ae a ee ee ee

—_ ha ~~ ee 2 : ae a me a

ence egeeteneeeyren Ap gt eee i nt aaa
nage. GNUsits be. Jolt ge.” Sit Sa ae

- 7" q a 7 o 7 - i q
Dell “es oe Pe hias aes ns 7 ia en aan _—