. 
ARTIFICIAL REFRIGERATION AND ICE MAKING. XLV. 
pheric pressure before it will evaporate at the freezing point of 
water. From these figures it will be noted that machines for 
making ice by the evaporation of water or ether must work with 
@ vacuum, their pumps exhausting their refrigerators to pressures 
below that of the atmosphere. 
THE LATENT HEAT OF LIQUEFACTION IN ITS APPLICATION TO 
REFRIGERATION, 
Although the low temperature at which a volatile medium may 
be made to boil in the coils of a refrigerator has a very important 
bearing on the production of cold, as in so doing it abstracts the 
heat necessary for its vaporization, there is another property of 
the medium that has been before referred to, which has a great 
deal to do with the results, and that is the latent heat of lique- 
faction, or the number of heat units that a pound of the medium 
will take up in passing from the liquid to the gaseous condition. 
To make the importance of this property clearer, suppose 
LATENT HEAT ,0F VAPORIZATION 
mate. BRITISH “THERMAL UNITS — 
With Principal Media in Refrigevafing Machines b 
a 3 E 
: w 
cl ae 7 
re od 
: n x 4 
z ‘ 5 4 
& 6 
x | te 
<q -——— Pea 
u 3 Zz 
Ww 32. nie Ue gaan ee ‘ oy ee ye | _ 
w 
: li 
See ee eel ee ee BEE 
a all pf} tt 
wu & 
a o . —_ oan Ee SS ee Se 
= « 
rad -10) 2 on Ser iee mer Me OS ss 
Fig. 6. 
