Dr. Hare's Improved Barometer Gage Eudiometer. 283 



Method of Operating. 



In the engraving, a leaden tube is represented as making a com- 

 TOunication between the gage tube and the cavity of the iron bottle, 

 through one of the valve cocks. Let it be supposed that, by means 

 of other valve cocks and tubes, like communications with an air 

 pump, and one or more reservoirs of gas, are under the control of 

 the operator. 



In order to analyze the atmosphere, he should have at his com- 

 mand a communication with a bell glass containing, over water, a 

 mixture of five parts of air and three of hydrogen ; also with a reser- 

 voir of hydrogen.* 



These arrangements being made, exhaust the bottles ; and admit- 

 ting two or*three volumes of hydrogen, exhaust again. By repeat- 

 ing this part of the process, nothing but hydrogen will remain in the 

 vessel. Let the zero of the descending scale be situated on a level 

 with the surface of the mercury in the gage tube, and then admit 

 eight volumes of the mixture, which will be known to have entered 

 when the surface of the mercurial column has fallen to eight on that 

 scale. All the cocks being closed, ignite the platina wire. The 

 explosion will be known to take place, both by the flash and sharp 

 noise which it produces. As soon as these indications are perceived, 

 the cock communicating with the gage may be re-opened. Nearly 

 three volumes of the mixture will be found to have disappeared, and 

 by the time that the thermometer indicates the temperature to be in 

 statu quo, it will be found that the deficit arising from the combustion 

 will a litde exceed that quantity. 



In analysing gaseous compounds of carbon with hydrogen, this 

 apparatus may be advantageously employed ; due proportions of the 

 carburet and of oxygen gas being previously mingled in an appro- 

 priate vessel over water. Suppose, for instance, olefiant gas were 

 in question ; one volume of it being mixed with four of oxygen : 

 after the explosion two volumes will be found wanting; because, in 

 one volume of the carburet, there are two of hydrogen and two of 

 carbon vapor. Each volume of the latter, will unite with one of 

 oxygen, without altering its volume. The two volumes of hydrogen 

 will take one of oxygen, and be condensed with it into water. Of 



* The necessary mixtures are effected either by means of the volumeters or 

 the sliding rod gas measure, of which I published engravings and descriptions in 

 this Journal, vol. 12, page 36, 1827; and in the London Philosophical Magazine 

 for 1828, vol. 32, page 126. 



