ON ARTIFICIAL REFRIGERATION. 



015 



Table of cryogcns and cryohijdrates. {Guthrie.) 



Namo of salt. 



Sodium broinido 



Ainmoniimi iodide 



Sodium iodidd 



Potussimn iodide 



Sodium chloride , 



Stroutiuiu chloride 



AiiiuioniuTii suli)li;ito. . 

 Auiniouium bnnnido.. 

 Ammouiuui nitrate . . . 



Sodiuiu nitrate 



Amnu)uium chloride.. 

 Potassium bromide ... 

 Potassium chloride . . . 

 Potassium cliromate . . 



Barium chloride 



Sti'ontium nitrato 



Magnesium sulphate. . 



Zinc sulphate 



Potassium nitrate 



Sodium carljonato 



Copper sulphate 



lion suli)hate 



Potassium sulphate . . . 

 Potassium l)ichiomate 



Barium nitrate 



Sodium sidphate 



Potassium chlorate . . - 



Ammonia alum 



Mercury perchloride. . 



ISTaBr 



NH4I 



Nal 



KI 



NaCl 



Sri I2 + CH2O 



Nn4SOj 



]SrH4Bi 



NHjNOj 



NaNO:j 



NHjCi 



KBr 



KCl 



KjCrOj 



BaCl2+2H20 



Srj N O3 



MgSOj + THsO 



ZnSOj+THjO 



KNO3 



Naj C O3 



CUSO44-5H2O 



PeSOj+THjO 



K2SO4 



KiCroOy 



Ba2N03 



lS"a2SO4-fl0H2O 



KCIO, 



Ai..X4ia;2S04+i2H20. 



H"CL 



"s — ^ 



c r. o 



« — 'J3 



ill 



41.61 

 57.6 

 59.39 

 51.72 



'27.' 5* 

 42. 2 

 32. 17 

 43.26 

 41.3 

 19. 27 

 31.80 

 20.07 

 30.41 

 24.0 

 25.91 



17.35 

 7.5 



"2." 88 



"4.2' 



"3.' 29 



Professor Guthrie has, from the evidence thus adduced, enunciatett 

 the general kiw that if we detiiie as similar salts either (1) those which 

 consist of the same acid united with bases belonging to the same chem- 

 ical group, or (2) those which consist of the same base united with acids 

 belonging to the same group, or those whose bases belong to the same 

 group, and whose acids belong to the same group — then, of similar 

 salts, the one icltich produces the f/reatest cold when used in a freezing-mix- 

 ture unites as a cryoliydrate icith the fewest molecules of ivater. And to 

 the following law there seems to be only one pronounced exception : The 

 temperature at ichich the cryohydrate is formed is the same as the tempera- 

 ture of the corresponding freenng-mixture. This hitter law, however, has 

 to be taken with reserve as far as those salts are concerned which, like 

 chloride of aluminium and chloride of magnesium, decompose water, and 

 also in regard to those bodies which, like chloride of calcium, unite with 

 water under the liberation of much heat. 



f L.— CHLORIDE OF CALCIUM ICE-MACHINE. 



The first practical cryogen-machine was patented in 1855 by Mr. C. 

 W. Siemens under the title " Improvements in cooling and in freezing 

 water and other bodies." In the apparatus required for these purposes 



