58 INJURY BY SMELTER WASTES. 
Sulphur trioxid.¢ 
Place from 1.50 to 2.50 grams of material in a nickel crucible of about 100 ce capacity 
and moisten with approximately 2 cc of water. Mix thoroughly, using a nickel or 
platinum rod. Add 5 grams of pure anhydrous sodium carbonate and mix. Add pure 
sodium peroxid (approximately 0.5 gram) small amounts at a time, thoroughly mixing 
the charge after each addition. Continue adding the peroxid until the mixture 
becomes nearly dry and quite granular, requiring usually about 5 grams of peroxid. 
Place the crucible over a low alcohol flame (or other flame free from sulphur) and 
carefully heat, with occasional stirring, until the contents are fused. (Should the 
material ignite the determination is worthless.) After fusion remove the crucible, 
allow to cool somewhat, and cover the hardened mass with peroxid to a depth of about 
0.5cm. Heat gradually and finally with a full flame until complete fusion takes place, 
rotating the crucible from time to time in order to bring any particles adhering to the 
sides into contact with the oxidizing material. Allow to remain over the lamp for 
ten minutes after fusion is complete. Cool somewhat, place the warm crucible and 
contents in a 600 cc beaker and-carefully add about 100 ce of water. After violent 
action has ceased, wash material out of crucible, make slightly acid with hydrochloric 
acid, and filter. Determine sulphates by precipitating with barium chlorid in the 
ordinary way. 
SOILS. 
Movrsture.@ 
Dry two or more grams in a tared platinum dish for five hours at the temperature 
of boiling water; cover the dish, cool in a desiccator and weigh. Repeat heating, 
cooling, and weighing at intervals of two hours, until the material ceases to lose 
weight. Weigh rapidly to avoid absorption of moisture from the air. The loss of 
weight is reported as moisture. 
Sulphur trioxid.¢ 
Digest 10 grams of soil on the steam bath for ten hours with 100 cc of hydrochloric 
acid (sp. gr. 1.115), shaking the flask every hour. Carry on this digestion in an 
Erlenmeyer flask, provided with ground-glass stopper ending in a reflux tube 20 
‘inches or more in length. Remove from the bath and allow to settle. Decant the 
solution into a porcelain dish, wash the insoluble residue onto a filter with hot water, 
and continue the washing until free of chlorids. Add the washings to the original 
solution, oxidize with a little nitric acid, and evaporate to dryness on a water bath. 
Take up with hot water and a few cubic centimeters of hydrochloric acid and again 
evaporate to dryness. Again add water and sufficient hydrochloric acid to effect 
solution, warm and filter, washing until free from chlorids. Again evaporate this 
filtrate to dryness, take up with a little hydrochloric acid and water, and filter to a 
volume of 500 cc. Take 200 cc of the above solution for analysis, evaporate nearly 
to dryness to expel the excess of acid, dilute with distilled water, heat to boiling, 
and precipitate by means of barium chlorid. Boil for about five minutes, allow 
to stand in a warm place overnight, filter, and determine the sulphur trioxid as 
barium sulphate. 
Arsenic. 
Weigh 1 gram of soil and treat with 25 cc of concentrated arsenic-free nitric acid 
in a small porcelain evaporating dish. Cover with a watch glass and digest on the 
steam bath for four hours, replacing the evaporated acid from time to time. Dilute 
the solution, filter, and wash residue. Return filtrate to the porcelain dish, add 
a Official and Provisional. Methods of Analysis, U. S. Dept. of Agr., Bureau of 
Chemistry Bul. 107, Rev. 
