228 ALKALIES. 



(b.) We let in a portion of oxygen, more or less, as we wish the 

 heat to be increased to any degree, till we reach the maximum. 



(c.) We ignite charcoal by the compound flame, and then shut 

 off the hydrogen, if we wish to have the effects of oxygen gas alone. 



(d.) This is beautifully seen in burning the metals ; we first raise 

 the heat by the compound flame, and when the globule of metal is 

 heated very intensely, we cut off the hydrogen and permit the oxy- 

 gen alone to flow, which at that high temperature sustains, and even 

 increases the combustion of the metals, not excepting cobalt, nickel, 

 silver and gold. 



4. Most intense light is exhibited, by bringing incombustible bodies, 

 such as the earths, and particularly lime and argil, in the form of a 

 pipe's stem, or of porcelain, into the focus : the naked eye cannot 

 endure the light : and in this focus the most refractory substances, 

 the rocks, the pure earths and the gems, are melted ; the diamond 

 alone excepted, which burns with great intensity, and is soon exhaled 

 in the form of carbonic acid gas.* 



THE ALKALIES. 



Preliminary Remarks. 



Several eminent writers at the present time, have broken up the 

 long established class of alkalies, and distributed them according to 

 relations derived from their composition : ammonia is described in 

 connexion with hydrogen and nitrogen, and potassa, soda and lithia, 

 under the metals. Similar remarks are applicable also to the earths. 

 This course is logical, but it is highly inconvenient; for it is scarcely 

 possible to take more than a few steps in the chemistry of particular 

 bodies, without calling in the aid of the alkalies, in our experiments 



* For the details of these and of numerous other experiments, see Dr. Hare's ori- 

 ginal pamphlet, and his and my own various memoirs in the Phil. Trans, of Phila- 

 delphia; in Tilloch's Phil. Mag. ; in the Annales de Chimie el de Physique ; in Dr. 

 Bruce's Journal, and in the American Journal. 



Dr. Hare remarks, (Comp. p. 77,) that excepting the republication of his memoir 

 in Tilloch's Phil. Mag. and in the Ann. de Chim. et de Phys. and a quotation of his 

 results in Murray's System of Chemistry, they had been generally neglected. 

 "Hence, (adds Dr. Hare,) a modification of the hydro-oxygen blowpipe was con- 

 trived by Mr. Brooke. Dr. Clarke, by means of this modification, repeated my ex- 

 periments and those of Prof. Silliman, without any other notice of our pretensions 

 than such as was calculated to convey erroneous impressions." 



I regret to say that this omission, although made known, was never corrected, and* 

 that the experiments of Dr. Clarke, most of which had been, years before, performed 

 and accounts of them published by Dr. Hare or myself, were entitled to no credit 

 for originality ; while the almost identity (in many cases) of the language in which 

 they were described, with that used by us so long before, proves that the results 

 with the two instruments were the same. 



It is not pleasant to transgress the kind maxim, nil de mortuis nisi bonum; but 

 truth obliges me in this instance to do it. 



The claims of Dr. Clarke respecting the compound blowpipe were entirely un- 

 founded. 



