CHEMISTRY. 



hausting and forcing pumps, one pair acting on 

 a cylinder (K) holding liquid sulphurous acid; 

 the other on the gasometer (ff) containing car- 

 bonic acid gas. These pumps are driven by a 

 steam-engine, and their purpose is to produce 

 a temperature of 140 Cent, in the tube A A' 

 (which contains the gas to be liquefied) by the 



alternate vaporization and liquefaction of the 

 sulphurous and carbonic acids. The various 

 operations will be understood from an expla- 

 nation of Fig. 2, which shows the apparatus in 

 section. Here K is a howitzer shell, which 

 contains TOO grammes of chlorate of potasli, 

 when oxygen is to be liquefied. A A! is a closed 



FIG. 1. PICTET'S APPARATUS (from a Photograph). 



iron tube, in which the gas becomes liquid ; 

 this tube is 5 metres in length, and 214 milli- 

 metres internal diameter. At E is a cock, also 

 a manometer graded to 800 atmospheres. The 

 tube is immersed in liquid carbonic acid (<?), 

 reduced to the temperature of 140 Cent, by 

 the action of the pumps. F\s a wooden case, 



is a similar case. D is a reservoir of liquid 

 carbonic acid, inclosed in a larger cylinder con- 

 taining liquid sulphurous acid, the temperature 

 of which is reduced by the action of the pumps. 

 G is the gasometer, which holds carbonic acid 

 gas; iff", reservoir of liquid sulphurous acid; 

 .P, one of the 4 pumps ; A', cock, which may 



packed with some bad heat-conductor, and H be opened to allow the liquefied gas to escape in 



. 2. SECTION OF THE SAME 



the direction shown by the arrows. The pumps 

 are kept at work for several hours before the 

 requisite temperature is attained, 140 Cent. 

 The pressure in the oxygen tube, when all the 

 oxygea-has been liberated from the chlorate 

 of potash by heat, is 320 atmospheres. These 

 two conditions coinciding, the cock is turned, 

 and a jet of vapor issues which is distinctly 

 seen to consist of two parts, viz., a central part, 



a few centimetres long, whose white color 

 gives evidence of liquid or even solid elements, 

 and an external part, whose blue color shows 

 the return of the compressed and frozen oxy- 

 gen to the gaseous state. But more palpable 

 evidence still exists of the liquefaction of oxy- 

 gen; for on substituting a very strong glass 

 tube for the iron one, M. Pictet has been able 

 to exhibit to the eye oxygen in the liquid state. 



