50 Mi'. A. W. Blyth. Observations on the [May 15, 



ordinary estimation of urea would have given low results ; it there- 

 fore appeared better to estimate the total nitrogen, and with certain 

 deductions described further on to calculate out the urea from the 

 data thus obtained. The total nitrogen was estimated by the moist 

 process of combustion, first proposed, I believe, by Vijeldahl (" Zeitech. 

 f Ur Analytische Chemie," Heft 3, 1883), and recently submitted to a 

 very exhaustive research as applied to urine by Dr. Petri and Th. 

 Lehmann ("Zeitsch. fur Physiologische Chemie," Band VIII, Heft 3, 

 1884). It is a very accurate method of determining the total nitrogen 

 in urine, in milk, and probably in most organic liquids, and will, 

 without doubt, be much used. 



Two grms. of the urine were placed in a flask, and 20 cub. centims. 

 of pure sulphuric acid added; heat was applied by means of a small 

 flame for two or three hours, at the end of which time crystals of 

 permanganate were added until the liquid was first decolorised, and 

 then given a distinct dark pink or red tint. On now alkalising with 

 pure soda, all the nitrogen present was distilled over as ammonia ; 

 the distillation being assisted by a current of hydrogen gas ; the 

 ammoniacal distillate was received in a known quantity of standard 

 decinormal acid, and titrated back by decinormal soda, usiug as an 

 indicator phenolphthaleln. 



The uric acid was determined in the usual way, viz., by concen- 

 trating half a litre of the filtered urine, strongly acidifying with 

 hydrochloric acid, and, after twenty-four hours, collecting the crystals 

 on a weighed filter. 



The hippuric acid was estimated by adding some recently calcined 

 magnesia to a litre of the urine, concentrating to a syrup, acidifying 

 the syrup with hydrochloric acid, aud extracting the acid liquid with 

 ether. 



The alkaloids (mostly kreatinine) were determined by acidifying 

 with sulphuric acid, and then precipitating by phosphomolybdic 

 acid ; the precipitate was decomposed by baryta at a boiling tem- 

 perature ; the phosphomolybdate of baryta filtered off and well 

 washed ; the filtrate containing the urine alkaloids and baryta was 

 saturated by carbon dioxide, boiled, concentrated, and filtered, the 

 filtrate being evaporated to dryness and weighed ; as there was still a 

 trace of baryta, it was necessary to ignite, re-weigh, and to take the 

 loss as representing the total alkaloids. 



The urea, as before said, was not estimated directly, but was calcu- 

 lated from the total nitrogen after subtracting the nitrogen in the 

 uric and hippuric acids and in the urine alkaloids ; it may be a trifle 

 over-estimated. 



For the total solids 5 grms. of the 'urine were evaporated at 100 C. 

 in a platinum dish, until the weight was practically constant. From 

 a larger quantity concentrated to a syrup, the mineral matter was 



