224 0" '^^ FroduB'wn of artificial Cold. 



Pr. Lovvitz's method is, to add at once the fait to the fnow;, the latter being previoufly 

 put into a convenient veflel. As the fait produces the greateft efFe£t whilft it retains the 

 greatefl quantity of water of cryftaliization, he prepares it during a freezing atmofphere, 

 pounds it, fifts it, and keeps it in clofe bottles, in a cold place. With a mixture of this 

 kind, Pr. Lowitz froze, in one experiment, 35 pounds of quickfilver. 



Pr. Lowitz obferves, that with the above precautions and management, it is impofliblc 

 to fail in the defign of freezing quickfilver with it. 



Pr. Lowitz found likewife, that the muriate of lime, prepared as above, produced 38 

 degrees of cold by folution ill water; that is, by adding 3 parts of this fait, in powder, to 

 2 parts of water, each at the temperature of -|- 36°^, the, thermometer funk to — i°j. 



Pr. Lowitz adds, that the muriate of lime which has been ufed for making frigorific 

 mixtures, may be procured again repeatedly, as fit as at firft for the fame purpofe, by 

 evaporation and cryftaliization. * 



Having given an account of Pr. Lowitz's experiments, I fhall now briefly relate the 

 refult of a feries of experiments made by myfelf, which occurred to me in confequencc of 

 Pr. Lowitz's difcovery. 



My fiift objeft was, to repeat the foregoing experiment under fimilar circumftances ; 

 but the thermometer (the temperature of the air and materials being -(- 32°) funk, in this 

 inftance, no lefs than — 48°. 



The liqucfaftion, in the above inftance, was remarkably fudden ; and the full cffe£b 

 was produced, as it were, in aft inftant. 



Secondly, with a view either of producing a very extraordinary degree of cold, or afcer- 

 taining the point at which this fait ceafes to produce further cold, I mixed the fame mate- 

 rials, previoufly cooled by art to 40° below o, when the thermorheter funk to 63"° below 0.+ 

 Thirdly, fome of the fame fait, in a cryftallized ftate, was fet out to deliquefce in the 

 open air: this liquor mixed with fnow, each at the temperature of + 32°, gave a cold 

 of — 20°. 



Hence it appears, that 52 degrees of heat were abforbed, or rendered latent, by the 

 liquefadlion of the fnow, and 28 by that of the fait, in the firft experiment ; that is, ia 

 the whole, 80 degrees. 



The muriate of lime ufed in the above experiments was prepared thus : muriatic acid 

 I part, and diftilled water 3 parts, were thoroughly mixed ; this liquor was then perfedtly 

 faturated with whiting, and, when clear, poured off. The mixture was afterwards eva- 

 porated; till it cryftallized in air at + 32°, (which happened when the liquor had been 

 evaporated to the confiftence of a thin fyrup,) and then reduced to fine powder. 



• The muriate of lime made ufe of by Prcfeflbr Lowitz, in thefe experiments, was obtained from the 

 refidue after the diftillaticn of cauftic ammonia. 



■f- In this inftance, as I afterwards found, the proportion of ihow, owing in part to a confidrrable por- 

 tion of the muriate of lime remaining frozen at the bottom of the veflel, and not mixing, was much to»^ 

 great. 



From 



