434 



LIQUEFACTION OF GASES. 



shall start, at what stations it shall stop, at what speed 

 it shall run, and has the general management of it, and 

 control over the persons employed upon it, represents 

 the company, and therefore that for injuries resulting 

 from his negligent acts the company is responsi- 

 ble. If such a conductor does not represent the com- 

 pany, then the train is operated without any represent- 

 ative of its owner. 



From this opinion four of the nine justices 

 Bradley, Matthews, Gray, and Blatchford 

 dissented. " We think," they said, " that the 

 conductor of the railroad train in this case was 

 a fellow-servant of the railroad company with 

 the other employes on the train. We think 

 that to hold otherwise would be to break down 

 the long-established rule with regard to the ex- 

 emption from responsibility of employers for 

 injuries to their servants by the negligence of 

 their fellow-servants." 



In 1880 an act was passed by Parliament in 

 England " to extend and regulate the liability 

 of employers to make compensation for per- 

 sonal injuries suffered by workmen in their 

 eervice." It does not set aside entirely the 

 rule that has grown up in the courts, but in 

 certain specified cases it abolishes the distinc- 

 tion between a workman and a stranger by 

 making employers liable to both on equal terms. 

 Efforts to secure similar legislation have been 

 made in New York, Massachusetts, and some 

 other States, but without success. 



LEMON-JUICE. See DKTJGS, NEW. 



LIQUEFACTION OF GASES. The experiments 

 of MM. Cailletet and Raoul Pictet on the 

 liquefaction of gases, and the apparatus they 

 employed, were described in the " Annual Cy- 

 clopaedia" for 1877. The processes have since 

 been much improved, the apparatus simpli- 

 fied, and more complete results obtained. M. 

 Cailletet, having failed to liquefy hydrogen un- 



der a pressure of one thousand atmospheres, 

 concluded that the result could not be accom- 

 plished by pressure alone, and was led to the 

 discovery of a fundamental property of gases 

 that had been overlooked. Andrews, experi- 

 menting on the compression of carbonic acid 

 at 13 C., found that the rate of condensation 

 increased more rapidly than Marietta's law 

 demanded, and progressively ; and that, at 

 fifty atmospheres, the gas suddenly became a 

 distinct liquid. At 21 C. the same result 

 was produced more slowly, and seemed to be 

 accompanied by a kind of preparatory stage 

 of more rapid condensation from some time 

 before the beginning of the change. At 32 C. 

 the signs of preparation were more marked 1 , 

 but instead of a distinct liquid, only wavy mo- 

 bile striae appeared on the sides of the vessel ; 

 while at higher temperatures there were nei- 

 ther striaB nor liquefaction. The temperature 

 of 32 C., therefore, marks a division between 

 the temperatures which permit and those which 

 prevent liquefaction, or is the critical point, 

 for carbonic acid. While a liquid usually has a 

 greater density than its vapor, it may be heated 

 in a closed vessel till it becomes as rare, or 

 rarer. At the same time the vapor accumu- 

 lating over it becomes more dense. Wlien the 

 densities of the two have become the same, 

 the line of separation between them will be 

 obliterated ; they will be no longer distinguisha- 

 ble, and they may be described as being in the 

 gaso-liquid state. All previous attempts to 

 liquefy air had failed, because they had been 

 made at temperatures above the critical point, 

 while the matter was still in the gaso-liquid 

 state. Cailletet and Pictet obtained their suc- 

 cess by reducing the temperature to below the 

 critical point and applying extreme pressure. 

 The liquefaction was, however, still not com- 

 plete, for the gases had not yet been seen col- 

 lected in a static condition and separated 

 from their vapors by the clearly defined con- 

 cave surface which is called a meniscus. A 

 more powerful refrigerant than had yet been 

 applied was found in the hydrocarbon ethy- 

 lene, which when liquefied boils at 103 0. 

 MM. Wroblewski and Olzewski, of Cracow, 

 with M. Cailletet's apparatus, in April, 1883, 

 by the ebullition of liquid ethylene obtained 

 a temperature of 150 C., and reduced 

 oxygen, previously compressed, to a fixed 

 liquid, with a clearly defined meniscus. Its 

 critical point was marked at 113 C., and 

 it boiled rapidly at 186 C. Nitrogen was 

 liquefied, under a pressure of thirty-six at- 

 mospheres, at 146 C. M. Cailletet sim- 

 plified the process by introducing tbrmene, or 

 marsh-gas, as a refrigerant which, although 

 less easily liquefied than ethylene, will pro- 

 duce by its ebullition in the air, without 

 the necessity of creating a vacuum, a temper- 

 ature of 160 C., under which both gases 

 are liquefied. In July, 1884, M. Olzewski 

 announced that he had produced by the ebul- 

 lition of liquid nitrogen in a vacuum a tern- 



