a heated tube, and then passed into alcohol for the purpose of retaining the products formed by heating the organic substances. The alcohol gradually changed its color and became dark brown. This experiment, though exceedingly imperfect, at present points, I think, to the possibility of estimating the purity of air by a direct determination of the quantities of those constituents which probably are the really injurious ones; while, at present, for the want of a more reliable method, we are obliged to be satisfied with determining the quantity of carbonic acid, and then drawing conclusions with reference to the amount of the organic matters present.
Various attempts have been made to simplify the determination of the amount of carbonic acid in air, so that even those who are not skilled in chemical manipulation might have a ready means for pronouncing upon the quality of air. The simplest of the methods proposed is the minimetric process of Lunge, which has been used to some extent in this as well as other countries. To show you, however, in what an unsatisfactory state this matter of air analysis still is, I will simply say that experiments undertaken, within a few months, by Hesse,[1] have shown that Lunge's minimetric process does not give reliable results, and hence conclusions reached from determinations made by this method are not to be regarded as final.
Another point still in dispute concerns the presence of carbonic oxide in the air. This lower oxide of carbon is undoubtedly poisonous, and can not be taken into the lungs without serious effects. The presence of only a small proportion of this gas will suffice to produce death. Now, if it could be shown that there are certain causes at work which apparently tend to introduce the gas into our dwellings and other buildings, alarm would naturally follow. Some years ago St. Claire-Deville, the French chemist, discovered that certain metals, when heated to red-heat, are porous for certain gases. This he found to be true of cast iron with reference to carbonic oxide. It is well known that in our coal-fires there is always formed a large quantity of carbonic oxide; and, further, that stoves and furnaces not uncommonly become red-hot. Putting these facts together, men became alarmed. Stoves and furnaces were regarded with horror. In the eyes of many they were looked upon as poison-generators of a very dangerous kind. Active diseases were, in some cases, believed to have their origin in the presence of carbonic oxide in the air; and, in cases in which active disease did not show itself, lassitude, headache, and other similar symptoms were supposed to be caused by the gas. There was a fashion, in some places, and particularly among those who prided themselves on "keeping up with the times," of referring every bodily affection to carbonic oxide when no other cause could be thought of, very much as, in days gone by, every disease which was not understood was classed under the general head "trouble with the liver."
- ↑ "Zeitschrift für Biologie," Bd. xiii., 395.
