132 Prof. Hare's improved Eudiometrical Apparatus. 



The receiver is a stout glass tube, which tapers from two 

 inches, in diameter, internally, to one inch ; being open at the 

 larger end, at the smaller end closed. This form was adopted 

 as combining strength, to resist explosions, with a capacity to 

 hold larger quantities of gas than have heretofore been ex- 

 ploded in eudiometers. It must be evident that the larger the 

 quantities of gas operated with, the less upon the whole will 

 be the influence of any minute leakage, or error in measure- 

 ment. 



The tube is cemented at the larger end into a brass fer- 

 rule, which is screwed into a casting of the same metal, fur- 

 nished with iron feet. Into the same casting, a brass plug 

 screws, through which are inserted stout wires, one of them 

 insulated, for producing galvanic ignition, in an arc of platina 

 wire, as already described in the case of my other eudiome- 

 ters *. 



With the gauge-tube, is associated a scale divided into 450 

 equal parts. Instead of inhaling successively due portions of 

 hydrogen and atmospheric air, as heretofore described, I have 

 found it better to mix them previously in known volumes, by 

 means of the volumeters, described in the preceding articles. 

 Having by the aid of one of those instruments made a mixture 

 of one part of hydrogen, with two of atmospheric air, it fol- 

 lows, that if 300 measures be taken by a sliding-rod eudiome- 

 ter, or other adequate means, there will be a mixture, in the 

 quantity so taken, of 200 parts of atmospheric air, and 100 of 

 hydrogen. In case equal volumes of these aeriform fluids be 

 mixed into one bell-glass, 200 measures would contain 100 of 

 each. This mode of procuring such mixtures, is preferable 

 from its saving trouble, and lessening the chances of error in 

 the measurement ; and because the gaseous fluids become more 

 thoroughly blended, — a result which does not follow their ad- 

 mixture as immediately as might be expected. 



Having prepared a mixture of two volumes of atmospheric 

 air with one of hydrogen, and the receiver being exhausted 

 as far as practicable, if any small quantity of the mixture be 

 exploded in it, by exciting ignition in the platina wire W, all 

 the oxygen will be condensed. The residuum, consisting of 

 hydrogen and nitrogen, will not interfere with the result of 

 any subsequent experiment, although the receiver should not 

 be thoroughly exhausted. Under these circumstances, let the 



* One of the greatest difficulties which 1 encountered, was in the imper- 

 fection of stop-cocks, in the common form. This I obviated by two con- 

 trivances of my own; one invented about sixteen years ago, the other in 

 the summer of 1825. Of these I shall publish a description, with engrav- 

 ings, as soon as I conveniently can. 



exhaustion 



