ALKALIMETRY. 245 



tightly connected with the graduated tube in such a 

 manner that a considerable interval may be left 

 between the ends of the two tubes. Upon this part 

 of the caoutchouc tube is fixed a clamp made of thick 

 brass wire, shown with its actual dimensions, in the 

 accompanying figure, so constructed that the caout- 



Fig. 32. 



chouc tube may be opened by pressing upon the two 

 ends of the clamp, and closed when the pressure is 

 removed. In order to use this tube, it is fixed in a 

 stand, in a vertical position, above the vessel contain- 

 ing the liquid to be tested. By pressing upon the ends 

 of the little clamp, the caoutchouc tube is opened, and 

 the liquid allowed to flow out, even in single drops, if 

 required. At the commencement of the operation, the 

 tube is filled with the test-liquid, a portion of which 

 is then made to flow out, by pressing upon the clamp 

 until it stands exactly at the zero of the scale. 



II. By determining the carbonic acid evolved. 



The carbonic acid is liberated from a weighed por- 

 .tion of the alkali, in an apparatus which is previously 

 weighed (together with the acid used to effect the 

 decomposition), and the carbonic acid determined from 

 the loss of weight. 



The apparatus employed for this purpose may be 

 21* 



