ARTIFICAL REFRIGERATION AND ICE MAKING. XLIX. 
figures regresenting the eee effect in thermal units as 
given by Siebel :— 
re suetion pressures in ths...) 4 _ 9 16 &. 24 a 45 
Corresp. temp. in refrigerator.. | — 20 10 Ges: 10 20 30 
ig | pein dl sping | page a of a cubic foot = ammonia | 
Fahr press in British Thermal Uni 
65 103 | 83°74 | i 28 | 54°88 | 68°66 | 85°15 | 106-21 
75 127 | 33°04 | 41°41 | 53°76 fi 83°44 | 104-09 
85 153 32°34 | 40°54 | 52°64 | 65°88 | 81°73 | 101:97 
95 184 31°64 | 39°67 | 51°52 | 64° yr 80°02 | 99°85 
100 | 218 30-94 | 38°80 | 50°40 | 63:10 | 78°31 | 97°73 
Shewing that with back pressures from 4 to 45 Ibs. the increase 
of condenser temperature from 65° to 105° only reduces the 
efficiency of a cubic foot of gas about nine per cent. 
THE ABSORPTION SYSTEM. 
Although compression machines now largely outnumber those 
Working on the absorption principle, and are daily replacing them, 
it must be remembered that the latter led the way and for a long 
time carried all before them. Introduced in 1858 by Ferdinand 
Carre of France, and in 1861 into Australia by E. D. Nicolle, 
this system was largely developed by the munificence of the late 
TB: Mort, and supplanted the ether machines of Harrison. 
In an absorption system an aqueous solution of ammonia is the 
medium used, instead of pure anhydrous ammonia. Taking a 
Solution of twenty-five parts of ammonia in seventy-five parts of 
water in a boiler or still, the application of heat will cause both 
8as and aqueous vapour (steam) to be given off in the proportion 
of, say, 90% of ammonia gas to 10% of steam or vapour. This 
Combined vapour is passed into a condenser under the pressure 
maintained in the boiler or still, which is dependent on the tem- 
perature and volume of the condensing water. By the combination 
. of this pressure with the transfer of heat to the condensing 
water the ammonia is liquefied. The liquid ammonia is allowed 
to expand in the coils of the refrigerator where it either freezes — 
or cools the substance it is employed to refrigerate. The gas being 
driven out of the boiler or still by the pressure generated, the 
Solution left, called the weak liquor, is then drawn out and cooled 
4—June 17, 1896, 
