<* 
62 INJURY BY SMELTER WASTES. 
dilute with 10 cc of arsenic-free water, a boil to break up the nitro-sulphuric acid 
formed. When cool, dilute with water and deliver into the Marsh-Berzelius apparatus 
previously described. 
Soluble arsenic. 
Weigh from 1 to 3 grams of the finely ground cattle food, according to the amount of 
soluble arsenic present, and transfer toa beaker. Extract on the steam bath with 50 
to 100 cc of water for four hours. Filter, wash, and evaporate the filtrate to a small 
bulk. Transfer to a 200 cc Jena flask and evaporate to only a few cubic centimeters. 
Add 25 ee of concentrated arsenic-free nitric acid and 5 cc of concentrated arsenic-free 
sulphuric acid, and proceed as in the preceding method for total arsenic. 
ORES. 
Sulphur.@ 
Treat 0.5 gram of the ore in a 6-oz. flask with 10 cc of strong nitric acid. Heat very 
gently until the red fumes have somewhat abated, and then add potassium chlorate in 
small portions at a time (about 0.2 to 0.3 gram) until any free sulphur that has separated 
is entirely oxidized and dissolved. The acid should not be boiled violently, nor 
should it simply simmer. When the sulphur has entirely disappeared, boil the solu- 
tion to complete dryness. (This may be hastened by manipulating the flask over a 
free flame.) After cooling cautiously add 5 cc of strong hydrochloric acid. If iron 
oxid, etc., still remains undissolved, gentle heat the hydrochloric acid mixture until 
solution is as complete as possible, adding more acid if necessary. Finally boil to 
dryness. Repeat this operation. Take up once more in 5 cc of hydrochloric acid 
and dilute with about 100 cc of hot water. Make alkaline with ammonia and then 
add 10 cc of a saturated solution of ammonium carbonate in order to convert any lead 
sulphate present to carbonate and thus render the combined SO, soluble as ammonium 
sulphate. Heat to boiling, allow ferric hydroxid, etc., to settle, filter, and wash very 
thoroughly with hot water, receiving the filtrate in a large beaker. 
Neutralize with hydrochloric acid and add 5 ce extra. Dilute to about300 ce and 
precipitate with barium chlorid in the ordinary way. 
Arsenic.@ 
Thoroughly mix 0.5 gram of the finely ground ore in a large platinum crucible with 
5 grams of a mixture of equal parts of dry sodium carbonate and potassium nitrate. 
Reserve a portion of the mixed salts for use asa cover. Heat the mass gradually overa 
Bunsen flame to complete fusion. Use a very low flame at first and take plenty of 
time to avoid loss of arsenic by volatilization. Finally heat to the full power of the 
Bunsen burner until thoroughly decomposed. The melted mass should finally present 
a smooth and homogeneous appearance. Cool, extract the soluble portion by heating 
with water, and filter and wash the residue with hot water. Drop a piece of litmus 
paper into the filtrate and make slightly acid with nitric acid, adding enough to dis- 
solve any precipitate that may have formed. Adda sufficient quantity of a solution 
of silver nitrate, which will usually cause a white precipitate of silver chlorid, and then 
cautiously add ammonia until, if arsenic be present, a reddish precipitate of silver 
arsenate appears. If too much ammonia be added the precipitate first formed will 
redissolve and may not be observed at all. Cautiously add dilute nitric acid until the 
red precipitate just redissolves. To the faintly acid liquid add a few cubic centi- 
meters of a strong solution of sodium acetate to replace the free nitric acid by acetic 
acid. All the arsenic will now at once precipitate as silver arsenate (Ag;AsO,). 
2 Low’s Technical Methods of Ore Analysis, 
