58 INJURY BY SMELTER WASTES. 



Sulphur trioxid.a 



Place from 1.50 to 2.50 grams of material in a nickel crucible of about 100 cc 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 

 0.5 cm . 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 cc 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. 



Moisture. (I 



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.a 



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 Bui. 107, Rev. 



i 



