Thursday, September 10, 2015
Widmark's per mille BAC unit, etc.
Widmark expresses the blood alcohol content as per mille, ‰, but this term can at first seem a little vague. By studying Table 1 in Neymark and Widmark, Kinetik des Aethylalkoholumsatzes (1935), we can assign a more meaningful unit to measure the BAC.
It appears from the data in the table that ‰ is equivalent to 1 gm/1000ml but since the density of water is 1 kg/liter this could also mean 1 gm/kg or 1 gm/1000gm which is unitless. Since by concentration we usually mean quantity per unit volume it seems more reasonable to use 1 gm/1000ml. When we do this the unit for the Widmark factor is liter/kg which is what we used before. Even though the factor here was obtained by experiments on dogs, we still get r = 0.7 liter/kg approximately.
Another expression, per os, used in Widmark, Konzentration des Alkohols (1914), means taken by mouth so it appears he drank the alcohol in a number of different concentrations but obtained similar results for the BAC vs time. In the experiments on the dogs the alcohol was administered by intravenous injection directly into the blood.