OP ARTS AND SCIENCES. lo 



who states that the compounds formed by zincic oxide and an alkali 

 were in general deliquescent and amorphous, but by using a potassic 

 hydrate solution of zincic oxide, and adding to it a small quantity of 

 alcohol, long needles were obtained, which he considered a " bi- 

 zincate of potassa." It was immediately decomposed by water into 

 zincic oxide and potassic hydrate. A few years later, in his article 

 in the Annales de Chimie et de Physique,* Fremy states that he has 

 met with great difficulties in obtaining the crystals, and hopes to re- 

 turn to the subject when he has determined the conditions under 

 which they are formed. Neither of his papers contains analyses, and 

 he has never published anything more on the subject, the reason for 

 which we can well understand after our unsuccessful attempts to pre- 

 pare potassic zincates. 



The work on the ammonic zincates has led to about the same un- 

 satisfactory results, no analyses of laboratory products having been 

 published; but Malaguti t gives an analysis of an incrustation found 

 upon a brick in the vault of a privy, which had the composition 

 3ZnO. 4NH 3 . 12H 2 0. 



The only other research which has approached this subject is one 

 by Prescott,* published in 1880, on the solubility of zincic oxide in 

 caustic alkalis. He found that more alkali is needed for complete 

 solution of the zincic oxide than would be required by the following 

 reaction, 



ZnS0 4 + 4 KOH = Zn(OK) 2 + K 2 S0 4 + 2 IT,0, 



but this excess was smaller in the case of sodic or ammonic hydrate 

 than with potassic hydrate; also that the excess of alkali could be 

 neutralized in such a solution without precipitating zincic hydrate, 

 until the amount was reached indicated by the reaction given above. 

 Addition of a large quantity of water precipitated the zincic hydrate 

 from the solution, even when it contained the excess of alkali. The 

 effect of dilution and temperature on the solubility were also studied, 

 but the determination of the composition of the substances formed did 

 not come within the scheme of his work. 



As, therefore, we could find in the chemical literature no analyses 

 of a zincate, with the exception of Malaguti's ammonic zincate, we 

 decided to take up the subject, and fortunately began our work with 

 the sodic zincate, since this proved to be the one of them all which 

 can be most easily prepared. 



* Ann. Chim. Phys., Ser. 3, xii. \ Cliem. News, xlii. 30. 



f Comptes Kendus, Ixii. 413. 



