232 Intelligence and Miscellaneous Articles* 



agglutinated and did not inflame; yet, on using double the quantity 

 of lamp-black, the pyrophorus obtained was extremely pulveru- 

 lent, and was astonishingly inflammable, so much so as to be almost 

 dangerous. 



This pyrophorus yields no sulphurous acid during combustion ; 

 when put into water, it gives no hydrogen, showing that there is no 

 uncombined potassium ; and when the solution is treated with an 

 acid, sulphuretted hydrogen is evolved, and sulphur precipitated. 

 Unlike common pyrophorus, it does not require moist air for its 

 combustion : the charcoal does not appear to be in a state of com- 

 bination, for the aqueous solution of the pyrophorus is not distin- 

 guishable from that of sulphuret of potassium, made without charcoal; 

 and this latter substance is so readily deposited in the vessel, as not 

 to indicate that state of minute division which is characteristic of 

 previous combination. 



The new pyrophorus, compared with the common, appears to 

 owe its greater inflammability to several causes : to its more mi- 

 nutely divided state, the absence of inactive earthy matter, and also 

 to the smaller proportion of sulphur. Sulphate of soda, used in 

 equivalent proportion, produces nearly the same effect as sulphate 

 of potash ; but sulphate of barytes did not at all answer. M. Gay- 

 Lusaac is of opinion that the action of potassium depends essen- 

 tially upon the great combustibility of sulphuret of potassium, and 

 its action upon water and air : alumina and magnesia appear only 

 to divide the combustible matter; but charcoal being itself com- 

 bustible, is not passive in the phenomena ; the combustion having 

 once commenced, it supports it. A very high temperature did not 

 appear to alter the inflammability of the pyrophorus, provided that, 

 during the cooling, the air was carefully excluded. — Ann. de Chim. 

 April 1828. 



Note. — Although we are by no means disposed to undervalue the 

 facts contained in the above statement, yet it will appear from the 

 following quotation from Dr. Thomson's System of Chemistry, vol. 

 ii. p. 541, that one of the principal of them does not possess all the 

 novelty which the author appears to suppose belongs to it. " Scheele 

 proved that alum deprived of potash is incapable of forming pyro- 

 phorus, and that sulphate of potash may be substituted for alum." 



R. P. 



EFFECT OF EBULLITION UPON CUPREOUS SALTS. 



It has been stated by Celin and Taillifert, that when blue or green 

 carbonate of copper is boiled in water, it retains its carbonic acid, 

 although it becomes black and anhydrous. On repeating these 

 experiments, M. Gay-Lussac found that the black powder is mere 

 anhydrous oxide of copper, and does not retain any carbonic acid. If 

 the boiling be stopped as soon as the carbonate becomes black, then 

 the product effervesces on the addition of acids ; this is derived from 

 the presence of some remaining carbonic acid. Acetate of copper 

 suffers similar decomposition by the same process. 



BORURET 



