352 RECORD OF SCIENCE FOR 1886. 



Boltzmanu lias established theoretically the possibility of basing the 

 kiuetic theory of gases upon the assumption of attractive forces only, 

 but under the express condition that these forces cease to act at infi- 

 nitely small distances. ( Wied. Ann., xxiv, 37 ; J. Phys., Nov., 1886, II, 

 V, 504.) 



Potier has discussed the law of freezing mixtures with reference to 

 the principle of maximum work, and shows that a direct combination 

 with absorption of heat is })0ssible only when the temperature is supe- 

 rior to that of dissociation ; while at a temperature inferior to that at 

 which dissociation commences, only combinations which evolve heat can 

 be formed. The inequality of Ciausius establishes thus a connection 

 between the principle of maximum work ef Berthelot and the fact that 

 a high temperature is more often required to begin the dissociation ; 

 and this without giving by itself alone the explanation either of tlie 

 principle of maximum work or of the effect of a high temperature. (J. 

 Phys., Feb., 188G, II, v, 53.) 



Pictet, in his memoirs upon freezing-machines, has called attention 

 to the remarkable properties, for i)urposes of refrigeration, of a mixture 

 of liquefied carbon dioxide and sulpliurous oxide gases, obtained by 

 compressing the product obtained by the action of sulphuric acid on 

 charcoal. The mixed liquid has this peculiarity', that its vapor press- 

 ure increases less rapidly with the temperature than that of sulphurous 

 oxide alone; so that it reaches this pressure between 25° and 30°, and 

 becomes less beyond it. The vai)or pressure of the mixed liquid is not 

 only much less than that of carbon dioxide, but actually less at temper- 

 atures above 25° than that of sulphurous oxide. The author thinks that 

 the two liquids form a conipound at high temperature which breaks up 

 at low ones. Since this liquid not only kills microbes, but extinguishes 

 fires, it is also useful for many other purposes. (Arch. Sci, Gen., xix^ 

 570; J. Phys., June, 1880, 11, V, 289.) 



Lightfoot has presented a paper on ice making machinery and appli- 

 ances to the Institution of Mechanical Engineers. He had designed 

 machinery for producing cold by the expansion of air after compression, 

 in which a weight of 1,000 pounds of air per hour can be reduced from 

 60° above to 80° below the Fahrenheit zero, the cooling water being at 

 60° F., with the expenditure of about 18 indicated horse-powers. A 

 novel application of freezing-machines was made in Stockholm in ex- 

 cavating a tunnel through gravel which was mixed with clay and water. 

 The innermost end of the tunnel was made into a freezing chamber, 

 and the gravel, etc., frozen ; then it was easilj^ removed. In this way it 

 was driven successfully for a distance of 80 feet. (Nature, May, 1886, 

 xxxiv, 45.) 



Horace Darwin has described an improved form of temperature reg- 

 ulator, constructed for use in the room at the Standard's oiUce, where the 

 comparisons are made. Its action depends on the variation of pressure 

 of a saturated vapor caused by a change of temperature. The liquid 



