160 



KRAEMER— DILUTE SULPHURIC ACID 



[April 20 



loss of sulphur by vaporization. The contents of the two U-tubes 

 were then poured into a graduate and the U-tubes, the bell jar and 

 the plate carefully rinsed with distilled water and the rinsings added 

 to the graduate, the contents of which was made up to about 200 or 

 300 c.c. One-half the quantity of solution was used for determining 

 the sulphuric acid formed, while the other half was used for deter- 

 mining the sulphurous acid present. 



To the portion used for determining the sulphuric acid 5 addi- 

 tional c.c. of tenth normal solution of sodium carbonate were added, 

 and the solution titrated with tenth normal sulphuric acid, using 

 methyl orange as indicator. The difference between the number of 

 c.c. of sodium carbonate solution used and the number of c.c. of 

 sulphuric acid solution consumed gives the equivalent of sulphur 

 acids formed. That the greater proportion of acids formed under 

 the conditions described is sulphuric acid, is shown by adding 

 barium chloride with an excess of hydrochloric acid to a hot solu- 

 tion, the precipitate formed being insoluble. The amount of sul- 

 phur converted into sulphuric acid is very easily calculated. 



The other half of the original solution was titrated with deci- 

 normal iodine solution using starch test solution as indicator, but 

 it was found that the proportion of sulphurous acid formed by heat- 

 ing or subliming the sulphur in the manner indicated was quite 

 small. 



In the following table the results of a number of experiments 

 are given : 



