1888.] 



A new Form of Eudiometer. 



385 



by means of weights, while the adjusting screw will enable its being 

 accurately placed under atmospheric pressure. 

 The analysis is made as follows : — 



We suppose that air for analysis has been shaken with barium 

 hydrate in a glass jar of a capacity of about 10 litres, and made 

 according to the form adopted by Dr. Angus Smith* for the 

 determination of carbonic acid in air by Pettenkofer's method. This 

 jar is closed by a tight-fitting india-rubber cap, which I cover with 

 several coats of copal varnish ; from this cap two short india-rubber 

 tubes project, each of these tubes being clamped by a jjinch-cock. 

 After the agitation is over, and when all the carbonic acid is taken 

 up by the alkaline solution, the fluid is poured out from the jar into 

 a glass-stoppered bottle holding about 100 c.c. This can be done 

 easily without letting any air into the jar, as the india-rubber cap 

 will collapse somewhat while the fluid is allowed to run out through 

 one of the india-rubber tubes in the cap, a very small quantity of 

 fluid only being left in the jar. The india-rubber tube is again 

 clamped, and the bottle holding the barium hydrate is sealed wdth 

 paraffine and left undisturbed for the precipitation of the carbonate 

 and subsequent analysis. 



The glass jar full of air free from carbonic acid, and absolutely 

 saturated with moisture, is placed under a funnel supported on a 

 filter stand, and the funnel is connected with one of the india-rubber 

 tubes projecting from the cap, while the other tube has a short piece 

 of glass tubing inserted into it, to which a longer india-rubber tube is 

 fixed. 



Everything is now ready for the determination of the oxygen of the 

 air contained in the glass jar. After turning the stop-cock in the cap 

 of the eudiometer, so as to allow the hydrogen gas to wash out the 

 steel tubes and top of the eudiometer, the latter is lowered in the 

 cylinder until the mercury is in contact with the cap, and therefore 

 very near to the stop -cock. The eudiometer is next connected by 

 narrow india-rubber tubing with the hydrogen receiver on which a 

 weight has been placed, and on opening the receiver hydrogen rushes 

 out, washing thoroughly the passage through which it will have to 

 reach the eudiometer, and driving out the very small quantity of air 

 contained in the steel cap between the mercury and the stop-cock. 1 

 found it convenient to stop the end of the \/" sna P e( ^ tube letting out 

 the gas with short india-rubber tubing and a pinch-cock. When a few 

 hundred cubic centimetres of gas have gone through, the three-way 

 tap is turned by one-quarter of a turn, so as to place the tube in 

 communication with the hydrogen ; it is now easy to rinse the eudio- 

 meter with that gas, by raising the eudiometer, and then giving the 

 three-way cock half a turn, so as to bring the instrument in comniuni- 

 * 1 Air and Rain,' 1872. 



