467 - ^^\ 



MISCELLANEOUS INTELLIGENCE. 



I. Mechanical Science. 



1. On the Compression of Gases, by M. Despretz. — Sulphurous 

 and sulphuretted hydrogen, cyanogen, and ammoniacal gases, are 

 not subject to the law of Mariotte. The difference becomes evident 

 under a pressure of two atmospheres, as may be seen by the 

 following table : — 



Xir Amraoalacal Gm. 



L819 1.850 



2.582 2.663 



3.863 4.132 



The gases were perfectly dry, and free from extraneous substances. 

 The graduated tubes containing them were surrounded by water, 

 so that the heat liberated could produce no effect. Hydrogen 

 accorded with air up to 15 atmospheres, and it was only under 20 

 atmospheres that the former was decidedly in advance of the latter: 

 on repeating the experiment, the tube burst at 28 atmospheres. 



These experiments show that the gases susceptible of being 

 liquefied, indicate a pressure, which appears to be greater than that 

 of the air, as the pressure is greater. It is probable that air itself 

 is not subject to the law of Mariotte at pressures but little increased, 

 but that can only be decided by measuring the pressure by a column 

 of mercury, and correcting the latter for the compression of the 

 metal. 



In a second communication^ the following is described as the 

 method employed by M. Despretz, Two graduated tubes, con- 

 taining one air, and the other the gas to be compared, were intro- 

 duced into a large tube containing water, each gas tube dipping 

 into a reservoir of mercury. The gases were perfectly dry; a 

 syringe was attached to the mouth of the large glass tube ; by 

 depressing the piston the water was compressed, and, consequently, 

 the gas and air in the tube. In this way, a uniform force was 

 applied ; but as the tubes were of the same diameter, and the gas 

 stood in them at the same height, it ought to rise equally in them, 

 in consequence of the pressure, if, at least, the gases were equally 

 compressible. But this did not happen, and, except hydrogen, ail 

 the gases were compressed more rapidly than air. To obtain the 

 value of the difference, Mariotte's law was assumed as correct, and 

 the elastic force of each gas calculated from the ditlerence of 

 volume which occurred. It was in this way that the numbers 

 above were obtained. 



M. Despretz is engaged in constructing an apparatus by which 

 the different gases may be compressed by a column of mercury, 

 and from which more accurate and advantageous results may be 

 expected. — Ann, de Chimie^ xxxiv., 335, 443* 



