On the ProduElion of artiftcial Cold, 227 



Series II. - 



Exp. ift. Muriate of lime - - 5, Ice-powder - - 4, at + ^2°, gave — 41 * 

 2d. — - ' - 4, ' - 3, - - 20 - - — 48 



3d. - - 4. '- - 3' - - 10 54 



4th. — — - - 3> --2-— 15-- — 68 



In the firfl experiment, the materials were mixed at the temperature of the air. 



In the fecond, they were previoufly cooled, by a mixture of muriate of ammonia, nitrate 

 of pot-afh and water; temperature of the air 52° ; the falts which formed the preparatory 

 mixture being recovered for ufe again, by evaporation. 



In the third, they were cooled previoufly, by a mixture of muriate of ammonia, nitrate 

 of pot-afli, fulphate of foda, and water; temperature of the air 50°. And, 



In the fourth, by a mixture of phofphate of foda, nitrate of ammonia, and diluted ni- 

 trous acid; temperature of the air 49°^. f 



Having concluded my experiments with the muriate of lime and ice^ I proceeded to try 

 the effects of this fait, prepared fo as to retain its folid (late during fummer, viz. of the 

 ftrength 1,490, by folution in water; and found that a mixture of this kind, produced 

 twenty-nine degrees of cold ; for, by adding 5 parts of the muriate of lime, in fine powder, 

 to 4 parts of water, each at the temperature of + 50°> I obtained a cold of + 21 : this 

 cffeft was not improved by the addition of other faks. 



Thcfe experiments were made in fuch an apparatus as I am going to defcrlbe, which 

 may at firft appear new, but, upon examination, will be found to be only a different mo- 

 dification of the vcffels reprefented in Fig. 3 and 4, Tab. XXIII of Phil. Tranf. for 1795J 

 (Philof. J. I. Plate XX.) and appears to me to have all the advantages that can be obtained 

 in .an experiment of this nature. 



The thermometer reprefented in the drawing was then placed in the tube of the upper veflel j and, when 

 the fnow was cooled to the utm ft, 'viz. to near 70 below 0, the cooled fnow was forced through into the 

 cup containing the acid, the veflels were feparated, and the fnow and liquor thoroughly mixed by means of 

 the thermometer contained in its glafstube ; the thermometer was then withdrawn from the tube, and ftirred 

 about in this laft or third mixture, which, in ten Seconds of time, indicated a cold of 91 'J below 5 

 tv"enty fecrnds more elapfed before the thermometer began to rife. The mouth of the cup in the veffel B 

 was, in this mftance,. clofed with waxed paper, in order that I might invert the veffel occafionally, to renew 

 the mixture in it ; and the cup itfelf was coated within-fide with wax, in order to defend it from the aftion 

 of the acid. 



* The fame experiratnt made at + 32», with fnow, (inftead of groimd ice,) gave — 40". 



t The compofition and application of thefe frigorlfic mixtures are given in Phil. Tranf. for 1795. 



(To be concluded in our next.) 



G g 2 DtreBionf 



