798 THE POPULAR SCIENCE MONTHLY. 



that had previously hindered successful working. The inflammability 

 of ether was nullified by the sulphurous acid ; a perfect lubricant was 

 obtained, and the substance had no corrosive action on the metals 

 employed. But the most interesting feature developed by the experi- 

 ment was that the ether was found to have the power of absorbing a 

 large proportion of the gas of the sulphurous acid. This is the charac- 

 teristic feature of the binary -absorption system, as Du Motay termed 

 his process. The ether, by absorbing the gas of the other constituent 

 liquid, reduces the mechanical problem to that of liquefying a gas 

 having a pressure not approximating that of sulphurous acid, viz., 

 fifty to eighty pounds or more per square inch, but barely more than 

 that of ether itself, viz., twenty pounds. The pressure of the com- 

 pound at rest, like that of ether, is nil. In other words, the ether is 

 found to have accomplished the greater part of the work, and a law 

 of nature governing the action of certain chemicals in combination is 

 availed of to reduce the mechanical labor of liquefaction to a mini- 

 mum. 



Since the death of Du Motay, w^hich occurred very soon after his 

 discovery, his associates, MM. Auguste Rossi and Leonard F. Beck- 

 with, have continued the experiments under the Du Motay patents, 

 with various other com^^ounds, and have accomplished the hitherto 

 unheard-of result of liquefying ammonia gas in the pump at a pressure 

 of thirty-five pounds per square inch. This is accomplished by com- 

 bining it with glycerine, a non-volatile, which gives up the ammonia 

 gas in the vacuum-pump, but, when it has reached a certain tension, 

 seizes it, so to speak, and renders it liquefiable at a fraction of its ordi- 

 rrary pressure. 



There are various other compounds capable of giving the same 

 results — an intense freezing power at a greatly diminished pressure, 

 and the peculiarities of various industries employing mechanical re- 

 frigerants can thus be consulted and met by the use of whatever com- 

 pound is found best adapted thereto. 



There are certain general features common to all the systems em- 

 ploying a liquid volatilizable in the vacuum-pump, but the peculiar 

 features of the binary absorption process admit of such a simplifying 

 of the mechanical appliances employed as to materially distinguish 

 their construction from that of other systems. 



The freezing agent, ethylo-sulphurous dioxide, or glycerine and 

 ammonia, or whatever be the compound employed, is placed Avithin 

 the " refrigerator," which consists of tubular coils immersed in an un- 

 congealable mixture. A double-acting vacuum-pump volatilizes the 

 agent in the refrigerator coils, and this is attended with the develop- 

 ment of an intense cold, which is communicated to the surrounding 

 mixture, and the latter, by means of a circulating pump, is made to 

 flow through a suitable tank containing vessels of water to be frozen, 

 or, if air-cooling only be desired, throi^gh iron tubing j^laced along the 



