On the Presence of Cyanate in the Blood

Abstract

IT has recently been asserted that considerable quantities of cyanate are found in the blood, namely 0*8-1*0 mg.HOCN per 100 cc.blood of the rabbit and cat [Montgomery, 1925].These findings are of very great interest, since cyanates and cyanic acid, on account of their chemical nature, might be considered as precursors of urea in the liver [Bollman, Mann and Magath, 1924] as well as of ammonia in the kidneys [Nash and Benedict, 1921].It might be presumed that, in neutral or in alkaline reaction, 2 mols.HOCN as well as 1 mol.NH4.OCN could give rise to urea, whilst cyanic acid, in acid reaction, is hydrolysed into ammonia and carbonic acid [cf.Werner, 1923].Nowadays, such findings arouse more than ordinary interest, since, in the course of the last years, the conclusion has been reached that blood does not contain such quantities of ammonia and carbamate as were previously assumed', and also since the theory that cyanic acid gives rise to urea is considered by some to be one of the most probable [cf.Werner, 1923, and Montgomery, 1925].However, in studying the ammonia formation in blood, I came to the conclusion that it was the same whether the blood, after collection, had stood either at acid or slightly alkaline reaction, so that it appeared unlikely that blood could contain such quantities of cyanate as recorded by Montgomery; for one would expect that the ammonia formation produced at acid reaction would be appreciably greater than that produced at alkaline reaction.I therefore tried at first to determine the velocity of decomposition of cyanic acid. 1 cc.N/5 KOCN was mixed with 99 cc."buffer mixture" of known reaction, and samples of 10 cc. were taken from time to time in order to determine the amount of ammonia formed, Folin's method being em- ployed for this determination.1 Concerning the ammonium concentration in the blood, cf.Barnett [1917], Nash and Benedict [1921], Henriques and Gottlieb [1924], Parnas and Heller [1924], Parnas [1925].According to Fauerholt [1924], the carbamate concentration in the blood must be very much smaller than the ammonium concentration.If, therefore, the ammonium-N concentration, according to the investigators mentioned above, is estimated at 0*03 mg. per 100 cc.blood at most, the car- bamate-N concentration in a bicarbonate solution like blood can, according to Fauerholt, only be 0-2 % of this, or 0-00006 mg. per 100 cc. of blood.Bioch.