On Kreatinins. 



501 



mode of formation of this compound appeared to me so remarkable 

 that I have prevailed upon my friend Mr. Herbert Jackson to execute 

 some microphotographs of the spherical mercury salt of the reducing 

 base of urine. 



This spherical mercury salt is very sparingly soluble in cold water. 

 When recently precipitated it dissolves with great ease in hydro- 

 chloric acid, but is insoluble or nearly so in acetic acid. 



Chemical Reactions and Decompositions of the Spherical Mercury Salt. 



Aqueous solution of ammonia does not blacken the spherical com- 

 pound, but if the salt be thrown into boiling water, the sediment 

 which remains undissolved is immediately blackened by ammonia- 

 water, so that a portion of the mercury in this compound is reduced 

 to the mercurous condition by contact with water at 100° 0. There- 

 fore, the spherical mercury salt must be washed with cold water, 

 and must be dried in vacuo over sulphuric acid, in order to avoid this 

 decomposition. 



Moistened with solution of potassium hydrate at the ordinary tem- 

 perature, the compound gradually becomes black by reduction, a 

 compound ammonia escaping at the same time in abundance. 



Suspended in cold water and treated with hydrogen sulphide, the 

 compound first becomes yellow and finally black (mercuric mercury), 

 and if the stream of gas be continued, nothing remains undissolved 

 but mercuric sulphide. The solution is acid in reaction, and reduces 

 both potassium picrate and cupric oxide in presence of potassium 

 hydrate at the boiling temperature (hydrochloride of the reducing 

 base). . ... 



Having convinced myself that the spherical compound is a definite 

 substance, I proceeded to ascertain the weight of it which is yielded 

 by a known volume of urine, and to subject the salt to analysis with 

 a view to ascertain its composition. 



Whilst determining the quantity of the spherical compound obtained 

 by precipitation from known volumes of urine, I was of course accu- 

 mulating a store of material from which to prepare large quantities of 

 the reducing base itself for subsequent examination. The method 

 which I adopted was as follows : — 



A quantity of fresh human urine is examined for albumen and sugar, 

 and, if found normal, its volume is exactly noted. The reaction to 

 litmus is then, ascertained, and also the amount of reduction of picric 

 acid (or cupric oxide) which it is capable of effecting. Next the 

 specific gravity of the specimen is observed, after which I add to it 

 one-twentieth of its volume of a cold saturated solution of sodium 

 acetate, and from one- third to one-fourth of its volume of cold satu- 

 rated mercuric chloride solution. There is no need to concentrate 

 the urine by evaporation. The mixture is now immediately 



VOL. xliii. 2 N 



