On the mutual Affinities of (he Earilis. 485 



termined by repeated trials. But before I draw any more general conclufions, I muft make 

 a few reflections on the manner in which we ought to confider this a£lion of the earths 

 upon each other. 



§ 3 , RefpeSiing the Manner in which thefe Phenomena ought to be wenved. 



Every cliemifl: mufl; be ftruck with the various points of refemblance which many of 

 thefe fa£ts feem to eftablifti between the alcalis and fome of thefe earths, and may be 

 tempted to think, that they might with equal propriety be placed among alkaline as earthy 

 fubftances, particularly if lime be joined with barytcs and ftrontian. 



Infadt, thefe three earths have an acrid tafte like the alkali^; the firft in the higheft 

 degree, the fecond rather lefs, and the third in a degree ftill lefs, but fo charadteriftic, that 

 it is from this that our firft idea of caufticity has been derived. 



Thefe earths are foluble in water nearly in proportion to their caufticity ; but it is the 

 efFeft, and not the dofe which forms the charafler ; otherwife we fliould have as many 

 clafles as bodies, which had not all their properties alike in the fame degree of power and 

 proportion of efFeft. 



The folutions of the two firft afford with eafe and in abundance very diftinft cryftals ; 

 It Is difficult to obtain a very regular cryftallization of lime ; but this folution, like that of 

 the others, depofits part of its earth by cooling in the folid form. It is a true cryftallization j 

 for cryftallization is not conftituted either by tranfparency, or the vifible regularity of 

 form. There is a real cryftallization whenever a fluid body pafles to the concrete ftate 

 by the rapid or flow abftraftion of the fluid which gave it its form, or which is the fame 

 thing, which held it in folution. It is ufual and very proper in the defcription of chemi- 

 cal phenomena, to diftinguifti cryftalline depofitions from thofe which are pulverulent; 

 but this is done to diftinguifti them, and by no means to point out a different nature. If 

 this were not true, we ought to reckon the metals uncryftallizable, becaufe they are with- 

 out tranfparence, or becaufe they exhibit only a rough exterior, when too <fudden cooling 

 prevents us from feeing the fymmetric arrangement of their particles. We mfght alfo 

 affirm, that the falts which afford the moft beautiful cryftals, do not in fa£t cryftallize 

 when the water of their folution is fuddenly abftra£ted by alcohol. Barytes itfelf here 

 affords an example, for its aqueous folution is precipitated by alcohol in the pulverulent 

 form. Here the cryftallization, inftead of being determined by the figure and attraftive 

 forces of the firft particles, depends no longer on thefe circumftances, but on the mode of 

 feparation of the difTolving fluid, and all the accidents which may render its produfts, ex- 

 ternally, of greater or lefs regularity with regard to our perceptions. If it were necefl"ary, 

 I might fupport thefe refle£lions by an experiment, which i$ the reverfe of the foregoing, 

 refpeftiiig bavytes. As there are circumftances in which it pafTes to the concrete ftate 

 without any vifible cryftallization, fo on the other hand I have afcertained, that there are 

 circumftances in which lime may be brought to the cryftalline ftate. For this purpofc, it 

 is necefl*ary only that lime water ftiould be diftilled in a glafs retort, and that new lime 

 Vol, III.—February t8oo. 3R water 



