264 



On Volumetric Estimation of Sugar. [Jan. 16, 



glucose prepared from starch, behaves like other varieties of grape 

 sugar, there is au intermediate product formed before the completion 

 of the process of conversion, which behaves in a different manner 

 from invert sugar, grape sugar, and sugar of diabetes. Estimations 

 made with the ammoniated copper liquid coincide with those made 

 with. Fehling's solution without the presence of ammonia, and the 

 addition of potash to the ammoniated liquid produces no modification 

 of the result. 



In order that the ammoniated copper liquid may be brought to the 

 same standard of sugar value as Fehling's solution, and it is desirable 

 that this should be the case, the proportion of copper must be in- 

 creased so as to give 6 atoms against 5. By taking 120 cub. centims. 

 of Fehling's solution, 300 cub. centims. of strong ammonia (sp. gr. 

 *880) and making up to a litre with distilled water, the proper pro- 

 portion is obtained, and the ammoniated liquid gives results corrobo- 

 rated in accuracy by the balance, and coinciding with those obtained 

 by Fehling's solution employed in the ordinary way. 



As a minor point it may be remarked that the diluted state pre- 

 sented by the ammoniated liquid offers an advantage by diminishing 

 the liability to error arising from any want of absolute precision in 

 measurement. 



Twenty cub. centims. of the ammoniated copper solution, corre- 

 sponding with. "010 grm. sugar, having been run in from the burette 

 containing the test, the flask is adapted to the cork attached to the 

 delivery tube of the other burette containing the saccharine product 

 for examination. The flame of a spirit lamp is then applied under- 

 neath, and the contents of the flask brought to a state of ebullition 

 and allowed to boil for a few minutes in order to get rid of the 

 presence of air. The saccharine product is now allowed to drop from 

 the burette until the blue colour of the test is just removed, and a 

 perfectly colourless limpid state produced. 



On account of the ammoniated copper solution used being only 

 equivalent to 2 cub. centims. of Fehling's solution, it is necessary 

 that the product to be examined should not be in too concentrated a 

 form. For delicate observation it is convenient that the dilution 

 should be such as to require the employment of from about 10 to 20 

 cub. centims. to decolorize the 20 cub. centims. of the ammoniated 

 copper solution. 



The ammoniated copper solution enjoys the advantage of possessing 

 a self-preservative power. It is well known in the case of Fehling's 

 solution that, in the course of time, not only does the liquid become 

 impaired in stability, but actually reduced in strength, by the spon- 

 taneous deposition of a certain amount of suboxide. Not so, how- 

 ever, with the ammoniated liquid. Here the conditions are such that 

 under exposure to air the copper cannot fail to remain in solution and 



