III. ANALYSIS. 625 



of the tubes E and F are, once for all, moistened with distilled water by the 

 introduction of a few drops into each, through the stop-cock on e and the 

 stoppered funnel i. The reservoir, previously filled with mercury, is now 

 placed in communication with the tubes E and F, and is raised until the 

 mercury flows from the cock on e, which is then shut, and rises into the cup 

 i, the stopper of which is then firmly closed. The absorption tube I, being 

 now filled with quicksilver, and attached to e by the screw clamp p, the 

 instrument is ready for use. 



With a proper supply of water the temperature of the gas remains constant 

 during the entire analysis, and therefore no correction on that score has to be 

 made. The atmospheric pressure being altogether excluded from exercising 

 any influence upon the volumes or pressures, no barometrical observations are 

 requisite ; and as the tension of aqueous vapour in E is exactly balanced by 

 that in F, the instrument is in this respect self correcting. 



The readings of pressures in this instrument give, without any calculation 

 or correction, the true volumes of the gases, and as the manipulations are very 

 simple, the analysis of even a complex gaseous mixture is made very rapidly. 

 Thus the determination of the separate constituents of a mixture of carbonic 

 anhydride, oxygen, hydrogen, carbonic oxide, marsh gas, and nitrogen can be 

 made in about two hours. 



2456a. Apparatus for Analysis of Gases. Modification 

 of that described by Frankland and Ward. For full description 

 see Journ. of Chem. Soc. 1869 [2], vii., 313. Prof. H. McLeod. 



2456n. Doyere's Apparatus for G-as Analysis. 



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



This apparatus consists of a vessel for water and mercury, a telescope, a 

 sheet of plate glass with levelling screws, a transfusing pipe, a detonating 

 eudiometer, and a mercury cistern which is used for the transfusing of the 

 gas. 



The vessel for water and mercury is formed of four plates of glass set in 

 a brass frame and resting on a cast-iron slab. Through this latter is nn 

 aperture leading to a cistern which projects beyond the vessel, and rises five 

 centimeters above the slab. The latter rests on four feet and stands on a 

 plate levelled by screws. The mercury is poured in by the exterior aperture 

 of the cistern until it has risen one centimeter from the bottom of the vessel ; 

 the vessel is then filled with water from above, up to f of its height. The 

 mercury bearing the mass of water rises about 1 centimeters through the 

 exterior aperture of the cistern, and the levels of the two liquids are esta- 

 blished permanently. The graduated tube is put in its place, by making its 

 lower aperture rest in a small iron spoon filled with mercury. By this 

 arrangement the spoon and the tube can traverse the whole mass of water 

 and reach the mercury in the basin, without any of the water penetrating into 

 the interior of the tube. The tube is held by brass pincers, which allow of the 

 reading being made along the whole length of the tube, and consequently of 

 the measurement of even the very smallest volume of gas. The pincers are 

 supported by a rod clamped to a gallows which can be moved vertically by a 

 rack and pinion outside of the vessel. The tube can thus be adjusted to 

 any required height. 



The stand of the telescope is formed of two tubes sliding one within the other, 

 with a rack and pinion ; at the top of this sliding tube is fixed horizontally a 

 telescope with a micrometer eyepiece. This micrometer allows of the fractions 

 of divisions being measured with great precision. The stand of the telescope 

 is fixed to a tripod furnished with levelling screws. In order to increase the 



40075. K r 



