Scientific Intelligence. 177 



Neither is aluinine essential ; for I prepared a very good pyro- 

 phorus with 1 atom of sulphate of potash, 3 atoms of sulphate of 

 magnesia and lamp black. 



Sulphuret of potassium, with one or several atoms of sulphur, or 

 even an oxysulphuret, not inflaming in the air when in mass ; and 

 the presence of aluraine and magnesia appearing to me to have no 

 other agency than that of dividing the sulphuret of potassium, it 

 seemed to me that I might advantageously replace these two bases 

 by charcoal. Accordingly with 25.3 of sulph. of potash 1 at. 



7.5 of lamp black 4 at. 



I obtained a sulphuret in mass, not inflammable ; but, by doubling 

 the dose of lamp black, I had a pulverulent matter, which inflamed 

 even in dry air v/ith astonishing rapidity. This matter is composed 

 of polysulphuret of potassium and potash intimately mingled with 

 carbon. It is more inflammable than common pyrophorus, because 

 the carbon being itself combustible, does not remain passive in the 

 phenomenon, like alumjne and magnesia ; the ignition having com- 

 menced, it feeds it. 



Sulphate of soda, treated with lamp black, gives a pyrophorus, but 

 sulphate of barytes yields none. — Idem. 



19. loduret of Calcium and Potassium. (J. de Phar. 1828. p. 

 44.) — In mixing together 1 J part of quick lime, which is to be slack- 

 ed in water, with 1 part of iodine, and 2 to 3 parts of water, there 

 is formed ioduret of calcium which remains in the liquid, and iodate 

 of lime insoluble, which mingles with excess of lime. 



In decomposing the ioduret of calcium by carb. of potash, we ob- 

 tain ioduret of potassium, pure. — Idem. 



20. Instructions relative to the art of Refining. Two memoirs 

 published in 1827 and 1828; by M. D^Arcet, Assay er of the Mint, 

 Paris. — The art of refining is that of separating gold and silver from 

 metals of less value, with which they are combined. It has been 

 practised from the earliest periods of the metallurgic arts. 



The method formerly used was to melt the ingot of metal to be 

 refined, with saltpetre, in order to separate the oxydable metals. It 

 was then converted into grains, which were heated in earthen vessels 

 at first with weak nitric acid, and in a second operation with that 

 which was more concentrated. The gold alone remained undissolv- 



Vol. XVIL— No. 1. 23 



