On Tribasic Phosphoric Acid. 



177 



the expiration of weeks. It is a hydrate still, and probably 

 contains two equivalents of water, and by heating it with an 

 alkaline salt it can easily be brought back to the flocculent, 

 gelatinous condition of the terhydrate. I will say more of this 

 peculiarity of the sesquioxide of iron hereafter. 



One of the two determinations of iron just mentioned was then 

 taken as representing the normal amount, and all the rest were 

 compared with it. Six other experiments were made in the 

 same way, differing only in this point, that before precipitating 

 with ammonia, to 3 and 4 was added one gramme of chloride of 

 sodium, to 5 and 6 one gramme of chloride of potassium, and to 

 7 and 8 one gramme of .sulphate of potassa. Again 50 cubic 

 centimetres (No. 9) were oxydized with hydrochloric acid and 

 chlorate of potassa — the solution precipitated by ammonia, the 

 precipitate washed out and weighed. In four experiments, 50 

 c. c. were reduced by zinc and sulphuric acid, and after adding to 

 12 and 13 a large amount of phosphate of soda, treated with a 

 standard solution of permanganate of potassa. In the two last 

 experiments, 50 c. c. were reduced by means of zinc and hy- 

 drochloric acid, and after adding a considerable amount of 

 phosphate of soda, treated with the same solution of perman- 

 ganate of potassa. 



As I have said heretofore, I will omit particulars and 

 the results, as follows : 



trive 



