c.c. (9.36 gr.) is the amount sufficient to produce death during the operation, that is, it is the experimental toxic equivalent.
For methyl alcohol, which Dujardin-Beaumetz and Audigé had found more toxic than ethyl, the results of Joffroy and Serveaux are most interesting. Although the method of purification had been greatly improved since the time of Dujardin-Beaumetz and Audigé, yet methyl alcohols coming from different sources were still shown to vary in their poisonous effects. Thus three alcohols from different sources gave the coefficient of toxicity for the rabbit as follows:
23.75 c.c. per kg.
26.75 c.c. per kg.
As an average of these three series we have an experimental toxic equivalent of 25.35 c.c. for methyl alcohol. The point of interest is not the degree of variation present, but the relatively slight toxicity of methyl alcohol when compared with ethyl alcohol. We shall see that the same is true when we study this as measured by another toxic limit.
For the entire series of primary alcohols which we have considered— methyl, ethyl and the higher alcohols—the following table summarizes the experimental toxic equivalent and its relation to molecular weight and boiling point.
|Chemical Formula||Molecular Weight||Boiling Point||Expt. Toxic
|Methyl||(CH3OH)||32||66.0° C.||23.35 c.c.|
|Ethyl||(C2H5OH)||46||78.4° C.||11.70 c.c.|
|Propyl||(C3H7OH)||60||60 97.0° C.||3.4 c.c.|
|(Iso)-Butyl||(C4H9OH)||74||117.0° C.||1.45 c.c.|
|Amyl||(C5H11OH)||88||88 138.0° C.||0.36 c.c.|
Such are the results when death is produced while the experiment is in progress. While this method has the advantage of rapidity it has also disadvantages.
It is clear that by adding alcohol up until the last inspiration more alcohol is given than is necessary to produce death. For this reason Joffroy and Serveaux realized that the experimental toxic equivalent has only a comparative value. For the exact measurement of toxicity the question is not how much alcohol will kill while the experiment is in progress, nor yet within a limit of 36 hours. The one question is, What is the amount necessary to kill?
(b) The True Toxic Equivalent