6 
BULLETIN 1316, U. S. DEPARTMENT OF AGRICULTURE 
Swain and Harkins (1$) also think that plants do not absorb 
enough arsenic from the soil to poison animals. However, Formad's 
(11) investigations in the smelter region of the Northwest have 
shown arsenic deposited on pasture grasses to be a great menace 
to animals. He found arsenic in the grass and hay in amounts vary- 
ing from 0.02 to 0.1 milligram of arsenious acid per gram of dry 
sample. Cattle, horses, and sheep feeding upon such grass and hay 
died by the thousands, evincing all the symptoms of arsenic poison- 
ing as developed in experimental treatments, and there seemed no 
doubt that arsenic was the cause of death. Harkins and Swain {2 If.) 
analyzed the animals fed on the grass and hay containing arsenic 
and found it in all parts of the animal tissues. 
METHOD USED IN ARSENIC ANALYSIS 
In the analyses for arsenic the generally accepted Marsh method 
and the modified Sanger-Black-Gutzeit method (W, p. 37) proved 
inadequate and time consuming as well as requiring an undue 
amount of attention. A combined modified method adapted from 
the methods of the Association of Official Agricultural Chemists (#, 
p. 56) and of Smith (37) was 
found effective and was there- 
fore used for all the analyses 
reported in the following pages. 
DESCRIPTION OF APPARATUS 
The apparatus was essentially 
of the type Smith has used (fig. 1) 
and consisted of a round 75-cubic- 
centimeter generating bottle con- 
nected through rubber stoppers by 
means of bent glass tubing to a 
horizontal heavy glass tube of 12 millimeters bore and 25 centimeters 
long, filled with absorbent cotton soaked in 5 per cent solution of 
Pb(CyE 3 2 ) 2 (to take up any H 2 S produced in the generating bot- 
tle). The other end of the horizontal tube was similarly connected 
to a receiving bottle of 125 cubic centimeters capacity. In the extra 
hole of the rubber stopper of the receiving bottle was placed a glass 
tube with sensitized paper (strips of stiff white paper soaked for an 
hour in 5 per cent HgBr 2 in 95 per cent alcohol) . The paper turns 
orange in contact with AsH 3 and serves as an indicator for the com- 
plete absorption of the gas. 
PREPARATION OF SAMPLE 
Two grams of finely ground barberry tissue were digested in a 
covered casserole over a low flame for 15 minutes with 5 cubic centi- 
meters of concentrated HN0 3 and 20 cubic centimeters of concen- 
trated H 2 S0 4 (As-free). To the solution, while hot, were added at 
intervals small amounts of KN0 3 until all organic matter was de- 
stroyed and the solution appeared practically clear. After cooling, 
the solution was diluted with 50 cubic centimeters of water and 
boiled until all the nitric acid was expelled. This is necessary be- 
Fig. 1. — Apparatus used in arsenic deter- 
minations. Generating bottle on left and 
receiving bottle on right 
