1879.] of Sugar by an Ammoniated Cupric Test. 273 



results. I have since learnt, however, that if the liquid to be examined 

 be dropped in slowly throughout, by which a longer time is occupied 

 in the performance of the operation, the result becomes to a certain 

 extent modified. It appears as though the test under the influence of 

 prolonged ebullition fails to possess the requisite stability. In the 

 case of Fehling's solution used in an ordinary way I have long known 

 that when in a diluted state, ebullition alone leads to the occurrence 

 of change, unless an additional amount of alkali be introduced. A 

 certain strength of alkalinity is required to give the requisite stability 

 to resist the effect of ebullition. With the ammoniated liquid, it is 

 to be remembered, a state of considerable dilution exists, viz., to the 

 .extent of 120 in 1,000. 



The introduction of a larger amount of fixed alkali into the 

 ammoniated liquid suffices to give it the power to resist the influence 

 of the variation in the method of procedure referred to in conducting 

 the analysis, and it is to make known the fact of the alteration being 

 required, that this communication is presented. 



If Fehling's solution be used in the preparation of the ammoniated 

 liquid, as I originally suggested, the amount of soda employed should 

 be doubled to meet the requirements. 



It was on account of Fehling's solution being so well known a 

 liquid, that I recommended the ammoniated test to be made from it. 

 Now that a modification has to be introduced, I may state that the 

 copper liquid I have generally been in the habit of using as a sugar 

 test is made with potash instead of soda, and contains a much larger 

 proportion of alkali than what is present in Fehling's solution. It 

 has appeared to me that the liquid thus constituted possesses the 

 advantage of greater precision of behaviour, and it may be used for 

 the preparation of the ammoniated test. The following is the com- 

 position recommended : — 



Cupric sulphate . . . . . . ... 34 "65 grms. 



Potassic sodic tartrate (Rochelle salt) . . 170 „ 



Potash .. .. ..170 



Water to 1 litre. 



120 cub. centims. of this liquid are mixed with 300 of strong 

 ammonia (sp. gr. 0'880) and water added to a litre for the am- 

 moniated test, 20 cub. centims. of which stand equivalent to 

 0'010 grm. of glucose. 



XXIX. " About some General Laws of Animal Life." By 

 Nicholas AVagner, Professor of Zoology, University, St. 

 Petersburg. Communicated by Professor Huxley, Sec.R.S. 



[Publication deferred.] 



