Artificial Cold. 271 



by Profeflbr Wolke, in which a hammer falls from a certain 

 point of a quadrant, fo as to ftrike an elaftic plate with a ve- 

 locity capable of precife determination. Thcfe experiments 

 relate to a fubje£l fo important that they nuift not be pafled 

 xmnoticed, however improbable it may appear that Galvanic 

 eleftricity flioiild have any material advantage over electricity 

 otherwife excited, and however we may be difpofed to believe 

 the report of other obfervers, that the relief is in general in- 

 confiderabie and only temporary. 



ARTIFICIAL COLD. 



Mr. Lowitz (Journal de Chimie et de Phyjique, by Van 

 Mons,) concludes, from various experiments on artificial 

 cold, of which a particular account is to be publiflied in the 

 TranfaAions of the Academy of Peterfbourg, 



1. That the principal caufe of the cold produced during 

 the folution of falls in water, depends '.ipon fome agency of 

 their water of cryflallization ; for falts deprived of this wa- 

 ter, inftead of producing cold, produce heat. 



2. Amongft the liquid acids, the muriatic acid is moft 

 efficacious for forming freezing mixtures; the nitrous acid 

 is next to it in order; and the fulphuric acid is leafl pow- 

 erful. 



3. The liquid acids produce cold only becaufe they oc- 

 cafion a quick folution of the fnow, or fait, of the freezing 

 mixture. 



4. Cauflic potafli and the muriate of lime furpafs very 

 much, as cooling agents, the acids and the other faline fub- 

 ftances. 



5. The befl proportion of the mixture of fnow and muriate 

 of lime, is two parts of the firft to three parts of the la(t, 

 mixed as accurately as poflible. 



6. Five pounds of muriate of lime arc fufficicnt to freeze 

 thirty-five pounds of mcrcurv. 



7. The deliquefceni falts arc much more proper for pro- 

 ducing cold than the cfllorcfcent falts. 



8. That the deliquefcent lalts may produce the highefl 

 poflible degree of cold, it is neceflarv that they contain the 

 grtatcft poffible (piantity of water of cryflallization ; and tliat 

 they be ulcd in fine powder. 



9. The fnow employed fliould be that which has ncwiv 

 fallen, light and drv; and the experiments f])ouId he made 

 at the connneneement of a I'rofl, and not during a thaw. 



10. It appears tliil the fu|)criority of the dcliquefcept 

 falls to the acids is owing to the circumfiaijce of their bc- 



A a 2 . coming 



