the bejl Methods tf producing Artificial Cold, jox 



tcrials to be cooled being exaftly adjufted, and, when they are to be mixed, precifely deter- 

 mined by the time employed in grinding the ice to powder. The proportions of fnow or 

 pounded ice and fait or falls may be guefled fufficiently near without weighing, unlefs in 

 very nice experiments. 



Imagining that a recapitulation of the different mixtures defcribed in my former paper 

 for producing artificial cold, brought into one view, might not be unufeful, I have fubjoined 

 a table of the fatts, their powers of producing cold with the different liquids, and the 

 proportions of each, according to a careful repetition of each; the temperature being 

 50 degrees. 



SALTS. 



Sal-ammoniac 5, nitre 5 



Sal-ammoniac 5, nitre 5, Glauber's falts 8 

 ' Nitrous ammoniac I 1 



Nitrous ammoniac I, fal foda I — 



Glauber's fait 3 — — 



Glauber's fait 6, fal-ammoniac 4, nitre 2 

 Glauber's fait 6, nitrous ammoniac 5 — 



Phofphorated foda 9 — 



Phofphorated foda 9, nitrous ammoniac 6 



Glauber's fait 8 



Glauber's fait 5 



Liquor. 



Water 



D. nitr. acid 2 



4 



4 



~ 4 



4 

 5 



4 



Marine acid 

 D. vitr. acid 



Temperature of 

 Cold produced. 



-f- Jo" 



+ 4 



+ 4 



7 



3 



— 21 



— + -j 



N. B. I have chofen the temperature of 50 degrees, becaufe the materials may at any 

 time, by immerfion in water drawn from a fpring, be cooled nearly to that temperature, 

 and the experiment for freezing with any of thefe mixtures commence there. 



At a higher temperature than 50 the quantity of the falts muft be increafed, and the ef- 

 feft will be proportionably greater : at a lower temperature diminiftied, when the effeft 

 will be proportionably lefs. 



It mud be obferved, that, to produce the greateft effedl by any frigorific mixture, the fait* 

 (bould be frefli cryftallized f, not damp, and newly reduced to very fine powder ; the vefier 

 in which they are made, very thin, and juft large enough to contain the mixture ; and the 

 materials mixed intimately together as quickly as poffible, the proper proportions at any 

 temperature (thofe in the table being adjufted for the temperature of 50° only) having been 



• Tlic fults from each of thefe may be recovered by evaporating the mix-ture to drynefs, and ufed again 

 repeatedly. 



N. B. The figures after each fait, and after the liquor^ fignify the proportion of parts by Troy weight to-be 

 (ifed i the trouble of weighing the water may be faved by obfcrving, that a full ounce of it by wine tneafure, 

 eorrefponds exactly wiK one ounce of it by Troy weight: likewilc it mud be noticed, when mote kinds of 

 falls than one are ufed, to add them to the liquor one after the other in the ol-dcr they (land in the table, be- 

 ginning on the left hand, and liirring the mixture well between each addition. D. nitr. acid is red fuming 

 nitrous acid two parts, and rain or ditliUed water onc.part by weight, well agitated together and become cool. 

 D. vitr. acid is ftrcng vitriolic acid, and rain or diftillcd water equal parts by weight, thoroughly mixed (very 

 cautioudy) and cooled. 



+ Soda, phofphorated foda, and Glauber's fait, arc bed cryftallized afrcfh, becaufe their efftft, cfpecially the 

 two laft, in the acids, depend; upoB the quantity of water they contain in a folid Itatc. 



previoufly 



