84 



Mr. E. Scliiinck on the Colouring and 



[Eecess, 



formed by the action of alkalies and oxgyen on indigo-blue; and though 

 there is not the least resemblance between the t\yo bodies, still the identity 

 in composition seems to indicate the possibility of a common origin. Is it 

 not possible, it may be asked, that the substance in urine which produces 

 indigo-blue may be in part converted, by a process of oxidation, into some 

 other substance which yields, instead of indigo-blue, a body having the 

 composition of anthranilic acid, i. e. of a substance which is formed by the 

 oxidation of indigo-blue 1 To me it seems very probable that this may be 

 the case. I am, however, far from attaching great importance to the com- 

 position of this substance as just given, for on a subsequent occasion I 

 obtained a product having exactly the same appearance as before, but a 

 different composition. On this occasion the method of preparation was 

 somewhat different. The urine was first mixed with acetate of lead as 

 long as a precipitate v/as produced. To the filtered liquid there was added 

 basic acetate of lead, which gave rise to a second precipitate. This was 

 filtered off, washed with water, and treated with an excess of dilute sul- 

 phuric acid, and the filtered liquid, instead of being boiled, was poured 

 into a shallow vessel and left to stand until, by spontaneous evaporation, it 

 had become tolerably concentrated. On now adding cold water, a brown 

 powder was left undissolved, which was filtered off, washed with boiling 

 wafer, and then treated with boiling alcohol as long as anything was dis- 

 solved. The hquid, after being filtered boiling hot, was evaporated, and 

 the residue was treated with a little cold alcohol, which left a brown 

 powder undissolved. This was pressed between folds of blotting-paper 

 and dried, after which it presented the same appearance as the first speci- 

 men. Its analysis led to the following results : — 



0-3730 grm. gave 0-8295 grra. carbonic acid and 0-1785grm. water. 



0"5750 grm. gave 0*2055 grm. platinum. 



The foraiula C.,, H ^. NO^g, with which these numbers correspond, re- 

 quires — 





Calculation. 



Experiment. 



c„ ... 



,. 168 



60-64 



60-65 



H„ ... 



15 



5-41 



5-31 



N 



, . 14 



505 



5-07 



o„ ... 



, . 80 



28-90 



28-97 





277 



100-00 



100-00 



Now the two form.ulae, though not identical, stand in a certain relation 

 to one another. If to the first there be added the formulae of benzoic acid 

 and of water, the sum will represent the second formula, for 

 H,, NO,, = C,, H, NO. + C,, 0^ + 2 HO. 



Benzoic acid is a product of decomposition of hippuric acid and other 

 animal substances, and it need therefore cause no surprise to find its ele- 

 ments among organic groups occurring in animal secretions, though of 

 course its actual presence in this case is doubtful. 



