J26 On t^e PreduBkn of artificial Cold; 



evaporation, before k be fet by to cool, In order to become folld, in eitber inftan'ce : tbfis, 

 ■when the muriate of lime is to be of that ftrcngth which is to be prepared and ufcd at the 

 temperature of + 3^°, the fpecific gravity of the liquor fliouid be, at the temperature of 

 + 80°, 1,450; and when of that ftrength to be kept and ufcd at the ordinary temfperature 

 of the air at any time, the fpecific gravity of the liquor (hould be 1,490, at 80° of heat. * 



The liquor, when fufficiently evaporated, (hould be fet by to cryftallize ; and the cry- 

 flallized mafs, as foon as cold, fliould be reduced to very fine powder, in a glafs or ftone 

 mortar. The muriate of lime, in its folid ftate, being a hard brittle fubftance, it is ncccf« 

 fary commonly to immerfe the veflel containing it in water fufBciently warm to loofen the 

 mafs, in order to remove it out of'the veflel, to pound it. 



When the muriate of lime is intended to be preferved for future ufe, the powder (hould 

 be put dire£lly into a bottle, and clofely (lopped from the air; for this fait is extremely 

 deliquefcent, and hence, a dry ftate of the atmofphere (hould be chofen for preparing it. 



Thefe experiments I (hall divide into two feries; the firft of which confifts of thofe 

 made with the muriate of lime prepared fo as to be ufed in nulnUr only, that is, of the 

 ftrength of 1,450. 



The fecond feries confifts of thofe made with the fame fait prepared fo as to be kept for 

 ufe at any time, the ftrength of which is ij490. 



Series I. 



Exp. ift. Muriate of lime - 3, Snow 2, - - at + 32" - - gave — 50° + 



2d. - 2, I, ----o---- — 66 



3d. - 3, I, -.--40..- 73 



4th. Diluted vitriolic acid 10, J — r— 8, ----68---- — pij 



Series 



• Muriate of lime evaporated to the ftrength of 1,400, gives (If cooled flowly In a cold air, ni'tK, + 20*) 

 perfefl cryQals; this is the fitted ftate of the fait for prcducing cold. 



■j- This experiment heing repeated, ufing ice-powder, (inftead of fnow,) gave — 51' } that !s, ice ground 

 to very fine powder with the inftrument defcrlbed in Pliil. Tianf. for 1795, page S?8S. (Philof. J. I. 498.) 



X Ccncentrated vitriolic acid 8 parts, water 4 parts, and reftifted fpirit of wine 1 part, mixed and coolett 

 previoufly to the tenaperature cf the air. ^ 



§ This fxperiment was made on the 10th of March laft, and conduced by a feries of three mixtures, 

 thus. The materials for the _/ifo?/^ mixture, confifting of muriate of lime and fnow, feparated ficra each- 

 other by an interverilng ftratum of fine fand, were cooled in a large veflel, having a partition in the middle 

 forming it into two compartments, to near 40" below 0, by mean* of a prior raixtuie of the fame m.7terials. 

 The materials for the yifoW mixture, cooled as above mentioned, were then mixed in each ci mparfment of 

 this double veffel, and let through an aperture at the bottom of each, (clewed till then by a temporary par- 

 tition,) into fuch an apparatus as that reprefented in the drawing, which contained the materials for the 

 /i;V</ or laft mixture, confifting of the diluted vitriolic acid and fnow, which had already been feparately 

 cooled in their refpe£live veiTeU, to near 40° below 0. 



The 



