viously weighed U-tube as indicated in Figure 2. This operation required about 10-15 minutes. The U-tube was again weighed. After reducing the volume of carbon dioxide used to standard conditions, the student was then in a position to calculate the gram molecular weight of the compound. As stated above, the usual laboratory precautions in manipulation must be strictly observed in order to obtain accurate results. The following figures are taken from among the best obtained by our classes : 44.06,43.73, 43.68, 44.0, 44.42, 44.57, 43.13, 44.80, 43.32, 43.42, 43.01.
From the data obtained in both parts of this paper it is clear that the student can easily establish the forinula of carbon dioxide as being COX and not some multiple of this formula.
Disinfectant Acts by Invisible Rays. That sodium hypochlorite, the common does not sterilize by direct disinfectant used in drinkina water and swimming pools, contact hut by means of gem-destroying invisible rays which it gives off when it comes into contact with organic matter, is the conclusion drawn from experiments made by French chemists, M.Philippe Bunau-Varilla and M. Emile Techoueyre, and communicated to the Academy of Sciences by M. Jean Perrin, Professor of Physical Chemistry a t the Sorbanne. It used to be thought that the purifying power of the compound was due to chemical reaction, as i t oxidized organic matter and decomposed itself. But while M. BunauVarilla was trying to determine the smallest amount of sodium hypochlorite necessary to sterilize a given amount of drinking water and not leave the usual chlorine taste, he found that the quantity necessary was too small to enter into any appreciable chemical reaction, and this fact suggested his ultra-violet ray theory. A series of experiments was then devised to prove or disprove the theory. A tube of quartz, which, unlike glass, is transparent t o ultra-violet rays, was filled witb a dilute solution of sodium hypochlorite and placed within a larger tube of quartz. The intersnace was filled witb water contaminated with colon bacilli, and the combination immersed in a bath of hypochlorite solution. An identical arrangement of quartz tubes, but lacking the surrounding disinfectant was prepared and the sets were allowed to stand 24 hours. I n order to find out if the bypachlorite had really given off death-dealing radiations, drops of the contaminated water were taken o u t of both tubes and "planted" in dishes of aelatina. sort of bacterial dinner pail-whex they were allowed to grow. The solu. tion containii the mast bacteria would grow the largest number of "colonies," and vice versa. I n 51 times out of 60 the contaminated water that had been surrounded for 24 hours by the hypochlorite solution grew fewer bacterial colonies than water not so exposed. It appears from these e x p e l k l ~ t sthat the hypchlorite gives off ultra-violet rays which, passing through the quartz, destroy the microbes that they reach.-Science ~
Sm'ce
The knowledge of nature as i t is--not as we imagine it to bcconstitutes true science.-Paracelsus
