466 M. J. Habermann on a Modification of Dumas's 



is admitted into the receiver, and tlie rest of the process carried 

 out as directed by Dumas. 



With substances of comparatively high melting-points and 

 vi^hich on cooling rapidly solidify, like benzoic acid, it is ad- 

 visable to make a slight alteration. 



The neck of the carefully cleaned balloon is not to be drawn 

 out into a capillary tube, but simply narrowed to the dimen- 

 sions above given, and connected directly with the aspirator. 

 There is then no danger of the solidifying distillate stopping 

 up the neck of the tube, as the solidification can only take 

 place in that part of the neck of the balloon which is situated 

 outside the oil-bath, where the substance can easily be 

 again liquefied by means of a spirit-lamp. 



Scarcely any remark is necessary respecting the calcula- 

 tion. Suffice it to say that, in the reduction of the volume 

 from the temperature at which the sealing is made, I take, 

 instead of the barometric pressure, the difference between that 

 and the reading of the manometer. 



The degree of applicability of the method here described 

 may be judged of by the following examples ; I will merely 

 premise that the time needed for the estimation, from the 

 moment in which the balloon filled with air is weighed, is 

 scarcely more than an hour. 



First Experiment. — Anhydrous Acetic Acid. Boiling-point 



137^. 



Amount of substance employed 0*6 grm. 



Weight of the balloon filled with air (P) ... 18-9572 gmis. 



Height of the barometer (B) 738'5 millims. 



Temperature (0 IQ'^'Q C. 



Weight of the balloon filled with vapour (Pi) 18-9340 grms. 



Height of the manometer (M) 488 milHms. 



Height of the barometer (Bj) 738*5 millims. 



Temperature (^i) 134° C. 



Capacity of the balloon (V) 120-5 cub. cent. 



Residual air 0-5 cub. cent. 



Calculated, Found. 



Vapour-density 3-536 3-528 



Second Experiment. — Aniline. Boiling-point 181° C. 



Amount of substance employed 0-92 grm. 



P =45-7606 grms., B =744-5 millims., t = 16°-2 0. 

 Pi = 45-5770grms., Bi= 744-5 millims., ^i=168° C. 



. M=;553 millims., Y = 353-8 cubic centims. 



