ON CAST IRON. ] g() 



the compounds that are confined to constant proportions, and 

 those that are subject to none, though both are the result of 

 the same power. 



Mr. Berthollet, in his Third Series of- Inquiries concerning 

 Affinities, expresses himself thus : 



" Proust asserts, that compounds, the proportions of which Objection of 

 are fixed, may unite with an excess of one of their elements eu 10i et ' 

 in an indefinite proportion ; without defining the characters, 

 that distinguish combination from this other kind of union. 

 It is obvious, that, in consequence of the latter distinction, it 

 would be difficult to object to him any observation, which he 

 would not find means to explain." 



If the preceding facts, to which many others might be p ro ust's an- 

 added, since the works of the elder chymists are loaded with swer - 

 them, sufficiently prove the existence of these kinds of union, 

 or solutions of compounds by their elements, or even by other 

 compounds ; it would appearto me superfluous to insistlonger 

 upon them : but I have been able to make them concur in 

 the explanation of certain phenomena, without any contra- 

 diction of principles. As to the characters that distinguish 

 them, or ally them to those compounds that range under the 

 laws of proportion, I am entirely of Mr, Berthollet's opinion. 

 But how should I define those characters? All the elements 

 of such unions are not sufficiently known. Chemistry not 

 having yet called for their being subjected to a particular 

 study, it is enough for the present to exhibit them as incon- 

 testable facts, till reflection determines their proper place in 

 the edifice of science. 



Hidrate of Iron. 



Mr. William Talaker, our collector for the Cabinet of a fine yellow- 

 Madrid, found a very fine yellow ochre in the mountains of ;>chrt '> con ; 

 Artana, in the kingdom of Valentia. It contains a little pa rbonate of 

 carbonate of lead, though there is no mine of that metal in lead - 

 the neighbourhood. This was taken up by weak nitric acid, 

 without altering the colour of the mineral. 



This ochre, freed from lead and carefully dried, was sub- ~ ,. ... .. 



. . . . O n distillation 



jected to distillation in a retort of ten inches capacity. The gav^ out 12 of 



aqueous vapour that arose completely expelled the air from water - 



' the retort, and with it about half an inch of carbonic acid 



