Mr Clark on a new Phosphate of Soda, 313 



been published by Professor Marx, as a proof that the arse- 

 niate of soda is not similiform with the rhomboidal phosphate 

 of soda; but it was merely an instance of a new arseniate of 

 soda ; and he did not obtain the rhomboidal one, only because 

 he did not use the proper means. But there were now two 

 arseniates of soda, only one of which corresponded in its water 

 and in its form with the phosphate. It remained to obtain a 

 second phosphate, corresponding in its form and its water, 

 with the second arseniate ; and this has been got, the very first 

 time it was properly sought for. Perhaps also, the discovery 

 may afford to Professor Mitscherlich some consolation against 

 the terrible sneers of certain chemical gentlemen of London, 

 who have written upon a subject, on which they were above 

 experimenting. The dazzling brilliancy of his discovery was 

 not to be beheld, or comprehended, by their eyes ; and, ac- 

 cordingly, they put forth their breath — but happily it was a 

 breath, destined to extinguish no light — save perhaps a 

 candle. 



Having^now obtained an arseniate and a phosphate of soda, 

 whereof each contained twenty-five proportions of water, and 

 each lost a portion of this water on exposure to the air, and, 

 also, an arseniate and a phosphate of soda, whereof each con- 

 tained fifteen proportions of water, and lost none by exposure 

 to the air ; I became interested in ascertaining whether the 

 former salts were changed by exposure into the latter. I 

 therefore subjected to experiment some crystals of efflorescing 

 arseniate and efflorescing phosphate of soda, which had been 

 pounded, and left, now for four weeks, spread out on a paper 

 in a large room, \\^hose temperature would vary from 52*^ to 

 62° Fahr. The following are the results of one experiment 

 on each effloresced salt : — 



VOL. VII. NO. II. OCT. 1827. 



