644 AGRICULTURAL ANALYSIS 



fur-salt wash : Total sulfur, sulfur as sulfids and polysulfids, sul- 

 fur as thiosulfates, sulfur as combined sulfates and sulfites, and 

 calcium oxid. Following are methods of analysis which give 

 good results : 



Total Sulfur. 22 Solutions Required. (a) A saturated potas- 

 sium hydroxid solution or a solution of sodium hydroxid con- 

 taining 100 grams to 100 cubic centimeters of water; (b) A 10 

 per cent, barium chlorid solution; (c) An approximately three 

 per cent, solution, of hydrogen peroxid free from sulfates. If 

 the solution contains sulfates add freshly precipitated barium 

 carbonate and shake occasionally for several hours, then filter 

 and use the clear solution. 



Determination. Place 10 cubic centimeters of the clear 

 sample in a 100 cubic centimeter measuring flask and fill to the 

 mark. Analyze 10 cubic centimeter aliquots of this solution. 

 Treat with three cubic centimeters of the caustic potash or soda 

 solution, following by 50 cubic centimeters of hydrogen peroxid 

 free from sulfates. Heat on the steam bath for one-half hour 

 exactly and then acidify with hydrochloric acid, precipitate with 

 barium chlorid in the usual way in boiling solution, and finally 

 weigh as barium sulfate. 



Sulfur as Sulfids and Polysulfids. 23 Solutions Required. The 

 same solutions are required as are used in the above determina- 

 tions with the following addition : 



Ammoniacal zinc chlorid solution. Dissolve 3.253 grams of 

 pure zinc in hydrochloric acid, supersaturate with ammonia 

 and make up to a liter. 



Determination. Pipette 10 to 25 cubic centimeters of the liquid 

 portion of the wash into a 100 cubic centimeter flask and make 

 up to the mark. Use 10 cubic centimeters of this representing 

 one to 2.5 cubic centimeters of the original solution, for analysis. 

 Add the ammoniacal zinc chlorid solution until slightly in excess, 

 as shown by the reaction of a drop of the solution with nickel sul- 

 fate. Place on the steam bath and heat until the odor of ammonia 

 becomes faint, filter, and wash. Transfer filter and contents to 

 a beaker, add about 10 to 15 cubic centimeters of a saturated 



n Avery, Bureau of Chemistry, Bulletin 90, 1905 : 105. 

 n Hay wood, Bureau of Chemistry, Bulletin 101, 1907 : 9. 



