622 SEC. 13. CHEMISTRY. 



third tube of the two stop-cocks, and serves to dry the globe and the tube of 

 the manometer, by taking care to turn the lower stop-cock in such a way as 

 to render impossible the rise of the mercury in the tube of the manometer. 



2456p. Hegnault's Apparatus for determining the 

 Tension of Steam at high pressure. 



GolaZj 24 Rue des Fosses, St. Jacques, Paris. 



This apparatus consists of four parts, 1, the boiler; 2, the reservoir of 

 compressed air ; 3, the manometer; 4, the force pump. 



1. The boiler is a cylinder with hemispherical ends. The upper portion is 

 traversed by two tubes fixed in it, and which are prolonged into the cylinder. 

 In these tubes are placed the thermometers indicating the temperature of the 

 steam. 



The cylinder is connected with a horizontal tube surrounded by another 

 cylinder which forms a refrigerator for the tubes, and is so placed as to be 

 able to furnish a constant current of water. At the extremity of this tube 

 is an arrangement for connecting the apparatus to the reservoir of compressed 

 air. 



2. The compressed air reservoir is of a cylindrical shape ; at the lower 

 part there is a junction for the attachment of a leaden tube which connects 

 it with the boiler. At the upper part are two stop-cocks connecting it 

 respectively Avith the manometer and the force pump. This pressure reser- 

 voir is suiTounded by a cylinder filled with water to keep it at an equable 

 temperature. 



3. The manometer is fitted with a cast-iron reservoir, and a force pump 

 with which the mercury is forced into the tubes ; a stop-cock is closed when 

 the mercury has risen to the height desired. A three-way cock allows the 

 compressed air to escape from the reservoir. 



The upper part of the pressure tube of the manometer is put in connection 

 with the compressed air reservoir by a small flexible leaden tube provided 

 with the necessary stop-cocks. 



4. The compression pump is worked by a shaft provided with a fly-wheel 

 and winch handle, and with it one man can readily obtain a pressure of 15 

 or 20 atmospheres. The valves are of leather, and are thus easily replaced 

 in case of derangement. 



For details of the apparatus and of the experiments made with it, see 

 " Memoire de 1' Academic", t. 21 (vol. 21). This apparatus was made by 

 the exhibitor for M. Regnault at. the time of his first experiments. 



2456q. Regnault's Apparatus for determining the 

 Tension of Vapour from to 100. 



Golaz, 24 line des Fosses, St. Jacques, Paris. 



This apparatus consists of a sheet iron vessel furnished with an agitator, 

 one side of it being formed of a pane of thick glass, so that all that is going 

 on inside may be seen. A cylinder is supported on an iron frame, upon 

 which are placed a mercury vessel, a screen, and an alcohol lamp ; two 

 barometrical tubes enter the vessel, one being a standard barometer, and the 

 other terminating at its upper end in a horizontal tube, whilst to the other end 

 a glass globe can be readily attached by means of a suitable mounting. In 

 the middle of the horizontal tube is placed a stop-cock by means of which 

 the globe and the barometrical tube can be emptied. In the globe is placed 

 the substance, the vapour tension of which is to be investigated. See " Mem. 

 de 1'Acad." t. 21, vol. 21. 



