2 Mr. J. Y. Buchanan on an Apparatus for Gas-analysis. 



and instructions, by Dr. Geissler, of Bonn ; and it is needless to 

 add that as a piece of glass workmanship it is a chef-d'oeuvre. 



Before describing it, it may be as well to state the objects 

 sought to be attained, when the motives in the design of the 

 various parts will be more apparent, and the measure in which 

 they fulfil their end more correctly appreciated. 



First of all, the size of the instrument must be reduced to a 

 minimum ; nor must its shape be so eccentric as to interfere with 

 its being packed into a reasonable space of symmetrical form. 

 Again, when packed it must be safe against rolling, and be easily 

 unpacked and mounted, and as easily dismounted and packed 

 away again. I wished further to be able to use eudiometrical as 

 well as absorptiometrical methods, using in the latter liquid re- 

 agents. The necessity for a special gas-analysis room had to 

 be dispensed with ; and, as before mentioned, the use of a mer- 

 curial trough was to be avoided. The advantages secured by 

 the peculiar way of packing, so that the case in which it is 

 packed when out of use forms its support, and a working tray 

 for saving spilled mercury when in use, were not contemplated 

 from the beginning, but suggested themselves only after the 

 glass work was finished, as until then the form and size of the 

 case could not be determined on. It was made for me by Messrs. 

 Kemp and Co., of Edinburgh ; and the workmanship is in every 

 way satisfactory. 



The apparatus consists essentially of two U-tubes. The one, 

 which according to precedent we may call the " laboratory tube," 

 is wholly of glass ; the other (the eudiometer) has the legs of 

 glass united by an india-rubber tube of suitable length. These 

 are affixed to mahogany boards iV and B, which fit into the 

 wings of the box C, where they are secured each by two bolts 

 (z, z) passing into the sides of the box. D is a strong mahogany 

 box for holding mercury. 



The glass U-tube, which for convenience we shall call A, as 

 well as the board to which it is attached, is 0*42 metre high ; 

 the shorter leg is 0*18 metre from the bend to where the capil- 

 lary tube is joined on, and its diameter is 0*02 metre. The 

 diameter of the capillary tubes is 0*003 metre. In the U-tube 

 B the eudiometer (q) is 0*17 metre from capillary to india-rub- 

 ber; the movable leg (p) is 0*34 metre long ; and the diameter of 

 both is the same as in A. The length of the box C is 0*45 

 metre, and the width and depth of each wing 0*195 metre and 

 0*105 metre respectively. The mercury-box D measures 0*12 

 metre by 0*10 metre by 0*08 metre, and when in use fits into 

 the place where it is represented in the figure. When dis- 

 mounted it is not packed in the case with the rest of the in- 

 strument. 



