538 On the occurrence of Organic Adds in Mineral Waters, 



but not produced by tbeni. M. Picard has completed the 

 proof of this theory. By the addition to blood of nitrate 

 of mercuiy he was able to separate every trace of urea from 

 it, and was thus able to compare the proportion of urea in arte- 

 rial with that in venous blood. The arterial blood of a dog con- 

 tained 00365 per cent, of urea, while venous blood contained 

 only 0'0186 per cent. In the human subject, he found that 

 blood which passes through the kidneys would furnish 28 grms. 

 of urea. Now the quantity of urea contained in the daily secre- 

 tion of urine amounts to 27 or 28 grms. The arterial blood 

 which arrives at the kidneys contains more urea than that which 

 passes from it, and the quantity of urea lost in traversing the 

 kidneys corresponds to the quantity found in the urine. Hence 

 the kidneys do not produce urea, but merely eliminate it. 



In the mineral water of Bruckenau in Bavaria, Scheerer* has 

 found formic, acetic, propionic, and butyric acids. The method 

 of detection was as follows : — Very large quantities of the water 

 were evaporated to a small bulk, and the precipitate which formed 

 was filtered off. The filtrate was distilled with excess of sul- 

 phuric acid, and the acid distillate neutralized with baryta. The 

 poixed baryta-salts were extracted with warm alcohol, which left 

 formiate of baryta undissolved; the presence of this salt was 

 established by the usual confirmatory tests. To the alcoholic 

 solution of the other baryta-salts sulphate of silver was added, by 

 which the silver-salts were obtained. 



From the properties of the silver-salts separated out by suc- 

 cessive crystallization, and from determinations of the silver 

 contained in them, evidence of the presence of acetic, propionic, 

 and butyric acids was obtained. Scheerer considers that these 

 , acids are formed by the gradual decomposition of certain con- 

 stituents of plants dissolved by the rain-water. He considers 

 that this change is promoted by the alkaline carbonates, which 

 are present in largest quantities in those waters which contain 

 the greatest proportion of these acids, and also by the presence 

 of the oxides of iron and manganese. The occuri'ence of organic 

 acids in mineral waters is more frequent than is generally thought : 

 Lehmann has recently found in the Marienbad water^ formic, 

 acetic, succinic, and even oleic and stearic acids. 



M. Belhommef has ascertained the presence of a colouring 

 matter in Monarda didyma, which from all its properties is 

 evidently carmine. It resides principally in the corolla ; and as 

 it is contained in tolerable quantity, it may be advantageously 

 extracted and had at a cheap rate. Samples of silks dyed with 

 it have given satisfactory results. 



♦ Liebig's Annaleuy gep<i, 1866, t Comptes Rendus, Aug. 18, 1856. 



