On the ProduBkn of artificial Cold. 223 



A eonfiderable acquifition however having been made, fince my laft Paper " On the 

 beft Methods of producing artificial Cold,"* by the difcovery that a neutral fait, but little 

 known, or attended to, by chemifts before, produced extraordinary effects of this kind 

 with ice, it could not fail of attracting my attention. 



Since the time I firft became acquainted with this circumftance, I have, as opportunity 

 offered, been engaged in making a variety of experiments with this iAx, which I flatter 

 myfelf, if the Society have not already received a communication on the fubjeft, may not 

 prove unacceptable. 



Before I relate my own experiments, it may be proper to premlfe a fliort account of 

 thofe of Mr. Lowitz, the author of the difcovery. 



The refult of Mr. Lowitz's experiments are, in his Memoir, f given according to the 

 fcale of Reaumur; but, m this, are throughout reduced to that of Fahrenheit. 



Mr. Lowitz, profeffor of chemiftry in Peterfburgh, having found, by an experiment 

 made in the winter of 1792, that cauftic vegetable alkali, in a folid ftate, produced a de- 

 gree of cold far exceeding any other fubftance before mixed with fnow, viz. 83 degrees, 

 determined to profecute the fubje£l ; and, upon refltClion, confidering that the deliquef- 

 cent falts were likely to be fitteft for his purpofe, fixed chiefly upon the clafs of muriatic 

 falts, or thofe which have their bafe neutralized by the muriatic acid. The refult of his 

 experiments was the difcovery, that cryftallized muriate of lime funk the thermometer 82 

 degrees; and that the other neutral falts of this clafs, though much inferior to that fait, 

 exhibited neverthelefs remarkable powers of the famekind. J 



Profeflbr Lowitz, in the Memoir alluded to, obferves that he has repeated my experi- 

 ments with chemical falts andy«aw, but could not produce a degree of cold below -f 2°^ 

 Here is evidently fome miftake ; for it is fufficiently known, that the novelty of my expe- 

 riments depends on the production of cold, without the ufe of ice in any form. § 



Pr. Lowitz having found by experiment that, at the temperature of + 2"]°, four parts of 

 muriate of lime to three of fnow produced a temperature of — 55°, and that an increafe of 

 the fait, even in the proportion of two to one, did not diminifh the effe£t, determined the 

 beft ^nd fure/I proportions to be, three parts of the muriate of lime to two of fnow. 



But, fince we fhall find hereafter the temperature of + 32° to be a more convenient 

 ttrm of comparifon, we may fairly ftate the fa£t thus ; that muriate of lime three parts, , 

 and fnow two patts, mixed at the temperature of + 32°, will give — 50°. 



The fnow, to produce the greateft effe£t, he fays, fhould be frefti-fallen, dry, and light 

 or uncomprefled ; and the fait perfedly dry, and reduced to very fine powder. 



• Phil. Tranf. for 1795, p. 270.. 



•f- See a tranflation from Crell's Chemical Annals for 1796, by Monf. Van Mons, Vol. XXII. p. 297, 

 of the Annates de Ch'imie, 



\ Profeffor Lowitz no fooner difcovered the great efficacy of the muriate of lime for this purpofe, than 

 he gladly rejefted the cauftic vegetable alkali, on account of its burning quality ; the difference being ont 

 degree only. 



^ See the table of frigorific mixtures. Phil. Tranf. for 1795, p. 27y. 



4 Pi^. 



