270 On the particular Properties of Roman Atum* 



there arc many of these phaenomena of which chemists will 

 long reinaHi spectators before any cause can be assigned for 

 them. 



IIow can \vc explain the pha-noniena of cementation^ 

 which converts into steel one of the extremities or the mid- 

 dle o'i a bar of iron subjected to this operation, while, cte- 

 tens purllwi, tlie remainrler continues to be iron ? 



How can \vc explain the phaniomenaof the combination 

 of hydroocn with oxygen, which, instead of giving birth to 

 an acid liquor, produces an insipid liquor? 



From the ana'.yfis of M. Vauquelm one might suspect 

 the ohservalion of M. Hassenfratz, and the experiment I 

 have mentioned, that the properties of Roman alum depend 

 on the state in which the alumine is found, and that there 

 must be a great ditTercnce between the alumine of Roman 

 alum and that of our natural or artificial alums. 



A volcano has been the crucible in which nature prepared 

 the Roman alum, while our furnaces, in which we prepare 

 that alumine, though brought to a strong red heat, are cold 

 in comparison of the conflagration produced bv a volcano*. 

 How much colder arc the turfy marshes in whic^h the latter 

 alum is prepared bv nature ? Every thing then proves that 

 the acli(«i of the caloric must have been very strong, and 

 that it is by it that a very- particular modification iias been 

 brought to the state of alum. This conjecture is still 

 further strengthened by anotlicr phenomenon — that exhi- 

 bited by the presence of potash in the earths of solfaterra. 

 This alkali has certainly not had there a vegetable origin, 

 and under this circumstance it cannot be considered but as 

 the result of a combination of the principles vv'hich the heat 

 may have called into action in some mineral substances. 



I shall conclude by observing, that the accuracy of 

 M. Vau(}uelin's analysis ought to subsist, because analysis 

 cannot follow these modifications, and that alumine, when 

 it issues by analytical means from its composition of Roman 

 alum, cannot appear to us but in that new state of modifi- 

 cation given to it by the rc-agent in taking it from its first 

 composition. I presume that this explanation will long be 

 the only probable one that can be given in regard to the 

 causes of the particidar properties of Roman alum, and that 

 further researches on this -iubject may have a great resem- 

 blance to those the object of which is to discover the phi- 

 losopher's stone. 



• If rhh opinion of ilie uuihot be correct, Iiow arc we to account for 

 minora! substances being fouml unfuscd in volcanic scoria which would 

 not itbibt the action of our furnacci .' — EblT^- 



I XLVIII. List 



