ioo Cellulose 



lected in portions of about 30 c.c., and when each such quan. 

 tity is obtained, a corresponding quantity of the acid is admitted 

 to the flask through the separating funnel . The distillation is 

 continued until a drop of the distillate ceases to give the well- 

 known reaction of the aldehyde (rose-red colouration with 

 aniline acetate, in presence of acetic acid). 



(b) Conversion into hydrazone. To ensure constant results 

 it is important that constant conditions be adopted. The 

 hydrochloric acid is neutralised with sodium carbonate, a 

 slight excess being used ; the solution is then made acid with 

 acetic acid. The distillate is made up to a constant volume, 

 and, as it is necessary to keep the proportion of sodium chloride 

 approximately constant, any deficiency of volume is made up 

 with a salt solution of corresponding concentration. 



The phenylhydrazine solution is made up with 12 grms. of 

 the base, 7*5 grms. glacial acetic acid, and water to 100 c.c. 



The formation of the hydrazone takes place according to the 

 reaction 



C 5 H 4 O 2 + Ph.N 2 H 3 = C 5 H 4 ON 2 HPh + H 2 O. 



and in any series of determinations with the same 

 substance, the quantity of phenylhydrazine solution necessary 

 to be added is, therefore, approximately known. The quantity 

 is controlled by testing the solution with aniline acetate, drops 

 of the solution being placed upon filter paper moistened with 

 the reagent. The solution is set aside for the separation of the 

 hydrazone, which is much facilitated by continuous stirring. 

 The hydrazone is collected in a filtering tube, containing a 

 perforated plate of platinum or porcelain upon which a circle 

 of filtering paper is laid, the filtration and washing of the pre- 

 cipitate being expedited by the use of the pump. The filter 

 tube, with its contents, is dried preferably in vacua at 60-70, 

 or in a slow current of dried air at this temperature. It is 

 then weighed. Having been weighed together with the filter 



