LIME-SULFUR-SALT MIXTURE 645 



solution of potassium hydroxid, and heat for some time. Add 

 50 cubic centimeters of hydrogen dioxid, free of sulfates, and 

 heat on the steam bath exactly 30 minutes. Acidify with hydro- 

 chloric acid and precipitate with barium chlorid in the usual 

 way. 



Sulfur as Thiosulfates. Solutions Required. Ammoma.cd.1 zinc 

 chlorid prepared as in the previous method, tenth-normal hy- 

 drochloric acid, and tenth-normal iodin prepared in the usual 

 way. 



Determination. Pipette five cubic centimeters of the original 

 solution into a 50 cubic centimeter flask and add ammoniacal zinc 

 chlorid until it is slightly in excess, as shown by nickel sulfate. 

 Make this mixture up to the mark, shake, and filter off through a 

 dry filter. To a 25 cubic centimeter aliquot of the filtrate add 

 methyl orange and titrate with tenth-normal hydrochloric acid to 

 exact neutrality. Next titrate the liquid with a tenth-normal io- 

 din solution. The reading thus obtained gives the total thio- 

 sulfates and sulfites ; since, however, the sulfites are present in 

 such small amounts as to be negligible the number of cubic cen- 

 timeters of iodin solution used may be considered to represent 

 only the thiosulfates. 



Sulfur as combined sulfates and sulfites. 24 Solutions Required. 

 The same solutions are used as are described in the preceding 

 method with the addition of 10 per cent, barium chlorid. 



Determination. Follow the preceding method to the point 

 where the thiosulfates have been changed to tetrathionates, and 

 sulfites to sulfates by the addition of tenth-normal iodin. Make 

 slightly acid with hydrochloric acid and precipitate the combined 

 sulfates and sulfites (now sulfates) with barium chlorid in the 

 usual way. 



Lime. 2S Solutions Required. Alkali and hydrogen peroxid 

 solutions prepared as described under total sulfur. Also a so- 

 lution of ammonium oxalate. 



Determination. Proceed as in the method for determining to- 

 tal sulfur to the point where all sulfur has been oxidized and 



14 Haywood, Bureau of Chemistry, Bulletin 101, 1905 : 9. 



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



