258 PKOCEEDINGS OF THE AMERICAN ACADEMY 



the gas through the capillary tube ee ; thence through the short U tube 

 A, containing chloride of calcium, to the combustion tube and absorption 

 apparatus ; and the gas is finally collected over water in the receiver 

 provided for that purpose. 



The introduction of a longer column of oxide of copper would 

 probably accomplish the same purpose with less expense ; but neither 

 expedient can be regarded as essential to the process. As the saving 

 of an analysis by the use of a longer column of oxide of copper would 

 only be occasional, the additional heat required, and consequent dis- 

 comfort occasioned by its continued use, would hardly be compensated 

 for. So that, while I would not, therefore, recommend the use of an 

 additional quantity of oxide of copper, I would also discard the other 

 expedient of collecting the gas over mercury or water, etc., unless the 

 saving of the surplus oxygen, together with the additional security af- 

 forded, should be considered of sufficient importance to recommend it. 

 As the passing through of the gas the second time requires no attention 

 after it is once started, and occupies but a short time, during which the 

 operator may attend to anything else, I much prefer, for myself, to 

 retain in use that part of the process. 



5. Some other less important peculiarities in the construction and 

 use of the apparatus will now be noticed, in connection with some re- 

 marks on the performance of the analysis. 



The posterior end*, of the combustion tube, as seen in the figure, is 

 bent obliquely upward, as in the common form, except that, instead 

 of being drawn out to a point, it is left of the full size of the tube. 

 The object of this form is to prevent, in a great measure, the escape of 

 oxygen during the time occupied in introducing the substance for anal- 

 ysis ; and also for greater convenience and security from loss in the per- 

 formance of this operation ; especially in the case of volatile liquids. 

 In the latter case," the neck of the bulb — which has previously been 

 provided with one or more scratches on its side near the end — is in- 

 troduced into the end of the combustion tube, and broken off by pressure 

 against the side of the tube ; the bulb itself is then allowed to drop in, 

 and the end of the tube immediately closed with a perforated cork 

 containing a glass tube, f, connecting it with the drying apparatus. 

 This connecting tube is constructed of hard Bohemian glass ; the 

 anterior end of which is drawn out to a short, blunt point, and the 

 opening nearly closed in the blowpipe flame, to the size of a small 

 needle ; the object of which is, to increase the rapidity of the flow of 



