2']6 On the ProduHion of artificial Cold, 



Class I. 



Temp, of mat. Temp, oi 

 Acids and falts. Ice. before cold. 



mixing produced 



Muriate of foda i, - ------.---- Snow 2, - - — 5° 



.' — ' — 2| Muriate of ammonia I, - - - _ - j, - _ — ij" 



— — — -^— lo, 5, Nitratcof pot-a(h 5, 84, - - — ii° 



■— — — s, Nitrate of ammonia 5, . - . - - — i2> - - —25"' 



Class II. 



Diluted vitriolic acid 2>* ---------- Snow f 3, +32° "—23' 



Concentrated muriatic acid 5, - -_-----. 8, +32° —27' 



Concentrated nitrous acid 4, t -------- y, +32° — 30° 



Muriate of lime 5,11 - ---------- 4, +32" — 40' 



3.** 2, +32° —50" 



Cauftic vegetable alkali 4, ---------- 3, +320 — 51* 



The above table is divided into two clafles. The firft clafs confifts of mixtures of falt& 

 and ice, in which the temperature of mixing is of no confequence, the cffed produced being 

 the fame at any temperature of the air : the falts fliould be in the ftate of powder. Ice 

 pounded fmall may be fubftituted, with equal effcft, for fnow. 



The fecond clafs confifts of fuch mixtures as will produce an efFedl greater^ the colder the 

 temperature is at which the materials are mixed, but in a diminijhing ratio ; ceaGng entirely 

 at that degree of cold at which the compofition itfelf free2e$. ft The falts fliould be in the 

 ftate of fine powder. 



N. B. The figures after the falts, or acidsi and Ice, exprefles the proportions, by lueight^ 

 to be ufed. 



• Concentrated vitriolic acid, diluted with half its weight of fnew, or diftilled water, and cooled. 



•}■ Snow that is frefli, dry, and uncomprefled, or fuch as has never been fubjeft to the effcfts of a temper- 

 ature lefs than freezing ; or, when fuch is not to be procured, ice reduced to powder, in the manner de- 

 fcribed in Phil. Tranf, for llSSy p. 271, may be fubftituted in its ftead, with equal effeft.. 



} Concentrated /a»»/«5 nitrous acid alone; or concentrated ]>«/* nitrous acid, diluted with one-fifth its 

 weight of fnow, or diftilled water, and cooled'. 



n Of theftrength of 1,490, at 80« of heat. 



*» Of the ftrength of 1,450, at 80° of heat. 



•ft The materials may be cooled, previoufly to mixing, when required,, by a frigorific mixture taken from 

 the table : for this purpofe, either of the mixtures in Clafs I. are convenient; particularly the firft, conflit- 

 ing of muriate of foda and fnow. 



In 



