814 Intelligence and Miscellaneous Articles, 



it is washed for a short time only, dissolved in muriatic acid, and 

 some alcohol added to the water with which it is diluted. On filtra- 

 tion, the sulphate of lime remains, and ammonia precipitates pure 

 phosphate of lime only. 



a. So-called neutral Phosphate of Alumina. — If a solution of alum 

 is mixed with one of ordinary phosphate of soda until the latter 

 produces no further precipitate, the filtered liquid, which, although 

 containing excess of the alkaline precipitant, reacts strongly acid, is 

 free from alumina, but contains a considerable amount of phos- 

 phoric acid. It might thus be readily imagined that the decompo- 

 sition which ensues here is similar to that in the case of silver, 

 where, as we know, (2NaO, H0)Pi,05 throws down 3AgO, P2O3. 

 The precipitate, when carefully washed and dried in the air, forms 

 a white, very loose and hygroscopic powder, which after having 

 been dried in a stove, loses 39" 17 per cent, of water at a red heat. 

 When dried in vacuo over sulphuric acid, it lost in four experiments 

 30'63-33*05 per cent. The results of its further analysis were, — 



With silica and With silica and With sulphuric acid 

 sulph. potash. carb. soda. and sulpn. potash. 



Phosphoric acid 35-07 37*55 41-85 38-62 36-92 



Alumina 26-34 26-14 24*50 



Water 39-17 33*05 



The quantities of oxygen in the alumina and phosphoric acid in 

 all these analyses approximate to the proportion of 3 : 5 ; the com- 

 pound is certainly = AI0O3, P2O3, but the quantity of water it con- 

 tains varies, inasmuch as the salt dried in the air contains 9 eq., that 

 over sulphuric acid sometimes 8, sometimes 7 and 6 eq. It is pro- 

 bable that the latter number of equivalents of water belong to a de- 

 finite hydrate, and the intermediate grades correspond to a mixture 

 of salts containing 6 and 9 eq. of water. 



b. So-called basic Phosphate of Alumina. — To procure this, the 

 previously described salt, whilst still moist, was dissolved in hydro- 

 chloric acid and precipitated with ammonia. The precipitate is 

 still more transparent and gelatinous than the former, and is washed 

 with greater diflliculty. 



The salt dried at 212° in a water- 

 The salt dried in the air yielded — bath gave, — 



with silica and With silica and With sulphuric acid 



carb. soda. carb. soda. and sulph. potash. 



Phosphoric acid 34-57 3 = 36-81 37-04 3 = 38-61 



Alumina 36-78 4 = 35-34 37-27 3736 4 = 3706 



Water... (28-92) 29-04 18 = 27*85 2379 15 = 24-33 



The compound is consequently 4AI2O3, 3Pj05, and contains when 

 dried in the air 18 eq. of water, at 212° however only 15 eq. 



Vauquelin has stated, that when phosphate of alumina is digested 

 with a solution of carbonate of potash, it is converted into pure alu- 

 mina. In repeating this experiment, allowing the digestion to con- 

 tinue for fourteen days and then boiling the mixture, it was found 

 that a part (one-fourth) only of the acid of the supi)osed neutral 

 phosphate of alumina was removed during its conversion into the so- 



