10 



Tranmction!>^. 



difficulties were met by shaking up witli slightly less magnesium-oxide 

 than was necessary to neutralize the free acid and then precipitating the 

 iron with potassium-ferrocyanide. 



Although the hydrochloric acid could be nearly neutralized by this 

 means, the chlorides so formed reacted with the mercuric cyanide, so that, 

 instead of a precipitate of HgS + S2, one containing a large proportion of 

 HgClo was obtained. This rendered the determination of the hydrogen 

 in the pentathionic acid more difficult and less reliable than in the absence 

 of HgCl,. It was therefore decided to be satisfied with the approximate 

 values for hydrogen already found, but to redetermine the sulphur and 

 oxygen. 



For this purpose 2,000 c.c. of the water was precipitated in the cold 

 with slightly less barium-chloride solution than was necessary to throw 

 down all the SO3. After standing for twenty-four hours, the barium-sulphate 

 was filtered off. The filtrate was divided into three portions, A, B, and C. 

 In A the small amount of SO3 still remaining was estimated by adding 

 excess of barium-chloride and allowing to stand for twenty-four hours. This 

 determination was made in the cold, because boiling causes slight decom- 

 position of pentathionic acid. In B, the total sulphur was determined 

 by oxidizing with bromine water and precipitating with barium-chloride. 

 C was boiled with mercuric cyanide, filtered, and the SO3 in the filtrate 

 determined by boiling with solution of barium-chloride. By subtracting the 

 amount of barium-sulphate obtained in A from the amounts found in B and 

 C respectively, the S and of the HaSgOg were readily calculated. The 

 results so obtained gave S5O5. go- 

 As the water is a very unusual one, the complete analysis will no doubt 

 be of interest. It is as follows : — 



9-24236 



