ARSENICALS. 
23 
Table 12. — Physical properties of commercial powdered calcium and lead arsenates and 
zinc arsenite. 
Sample 
No. 
Material examined. 
Total 
arsenic 
oxid 
(As 2 5 )in 
powders. 
Apparent 
density. 1 
Suspension proper- 
ties after stand- 
ing for 2 — 
10 
minutes. 
60 
minutes. 
59 
Calciumarsenate 
Per cent. 
45.37 
47.83 
40.38 
41.40 
49.40 
40.49 
39.19 
31.89 
32.93 
31.50 
32.90 
32.47 
32.75 
3 41.49 
Grams. 
254 
257 
364 
365 
422 
532 
567 
247 
249 
284 
306 
369 
747 
355 
Cubic 
centi- 
meters. 
245 
188 
365 
380 
170 
245 
170 
230 
270 
110 
265 
146 
88 
165 
Cubic 
centi- 
meters. 
200 
58 
do 
115 
97 
do 
145 
98 
do 
120 
24 
...do 
140 
57 
do 
57 
56 
do 
71 
85 
Acidlead arsenate 
167 
39 
do 
132 
83 
do 
123 
84 
.....do 
135 
38 
.....do 
90 
82 
do... 
60 
23 
77 
1 Weight of powder occupying a volume of 1,000 cc. without being jarred. 
2 Based on volumetric readings of 30 grams of powder, shaken with 500 cc. of water and allowed to stand. 
3 Arsenious oxid (AS2O3). 
In Table 12 the calcium and acid lead arsenates are arranged 
according to their apparent densities, the lightest ones first. The 
lightest powders usually remained suspended for the longest time 
(60-minute test) and the heavy powders settled most rapidly. More 
than 90 per cent of all the arsenicals tested passed a 40-mesh sieve 
after having been shaken for five minutes. These results are of no 
value and therefore are not given. It is believed that the fineness 
of powdered arsenicals, which are generally amorphous, can not be 
correctly determined by this test, since fine powders pack in a 40- 
mesh sieve. The fineness of relatively coarse arsenicals, such as 
arsenious oxid, can be determined by sieving. 
Microscopical examinations of the various arsenicals were made. 
A large number of samples of powdered calcium and acid lead arse- 
nates and one of zinc arsenite were blown from a dust gun. These 
dusts, collected on six or more microscopic slides placed at varying 
distances from the dust gun, were photographed. Then, using a 
high-power lens of the microscope, drawings were made by the aid 
of the camera lucida which made possible the determination of 
slight differences in the size of particles but did not give satisfactory 
information on the dusting or spraying properties of these products. 
Several samples of powdered lead arsenate and Paris green, 
examined under a magnification of 100 diameters, appeared to be 
amorphous. The samples of calcium arsenate contained a few 
small crystals, although the samples on the whole appeared to be 
largely without crystalline shapes. Four samples of arsenious oxid 
were examined under the microscope. Samples 19 and 27 consisted 
chiefly of small octahedral crystals; sample 37 contained somewhat 
larger crystals. 
