Bodily Labour upon the Discharge of Nitrogen, 459 



Chlorides. — None of the special methods in use for the estimation of 

 chlorides in urine are satisfactory. Direct titration with silver, with 

 potassic chromate as indicator, is practically worthless, and the time 

 required and the risks involved in the method of estimation in the 

 ash render it impracticable when time is of any consequence. I have 

 therefore adopted the simpler plan of diluting the urine with 5 or 

 6 volumes of water, and precipitating with argentic nitrate in the 

 presence of a minimum of nitric acid, and washing and weighing the 

 chloride formed. The results when the operation is carefully con- 

 ducted are most satisfactory. 



Sulphates. — These were estimated gravimetrically in the usual way 

 by precipitation from the boiling urine with barium chloride and a 

 minimum of hydrochloric acid. 



Phosphates. — The ordinary uranium process was used, and I need 

 only remark of it, the absolute necessity which exists for the use of 

 perfectly fresh ferrocyanide solution. In order to secure this I find it 

 best to keep a quantity of the finely powdered crystals, and dissolve 

 them as required on the testing tile. 



I have made no attempt to estimate any of the individual nitro- 

 genous bodies in the urine, but have confined myself strictly to the 

 consideration of the total nitrogen, and the variations which it under- 

 goes under various circumstances, without complicating the problem 

 by attempting to discriminate between the various bodies which go to 

 make up the total which, as a matter of fact, our present methods will 

 not allow us to do with enough accuracy to make the investigation 

 worth the immense amount of additional labour which it would 

 involve. 



Methods Used in the Analysis of Fmces-. 



The collecting apparatus has been already described, and I need 

 only now say of it that it was thoroughly satisfactory in every 

 respect. 



On arrival at the laboratory the cases are opened, the glass dish 

 and cover removed, and together with their contents carefully weighed, 

 the difference between the total weight and the weights marked on 

 the dish and cover giving the weight of the faeces. The cover was 

 then removed, and a sufficiency of methylated spirit poured upon them 

 to cover them. This completely destroyed all objectionable smell, 

 and rendered the material safe from decomposition. 



I did not estimate the nitrogen in each day's fasces, but divided an 

 experiment into three periods : the period before the work, the period 

 of the work, and the period after the work. Each sample as passed 

 was placed with the alcohol in a large porcelain dish over the water- 

 bath, and after being well broken up with a glass paddle, was rapidly 

 dried, and the residue by constant stirring reduced to a dry granular 



2 h 2 



