72 THE POPULAR SCIENCE MONTHLY. 



laboratories is not perfectly pure, but that it contains substances that 

 will change in time. These substances might be mineral or organic, or 

 even living organisms. Wishing to ascertain whether the last was 

 the case, I added to the water in one of the tubes 10 ooo of bichloride 

 of mercury, while I left that in the other tube unchanged. The small 

 quantity of bichloride did not at all affect the color of the water to 

 which it was added. In the course of six days the water which had 

 been left alone became blue-green, while that to which bichloride of 

 mercury had been added preserved a fixed blue, and exhibited no sign 

 of change for three weeks ; but, when the salt was put into the water 

 that had turned blue-green, that began slowly to turn blue again, and 

 this process continued for nine days, when it stopped, without the blue 

 color having been quite restored. Inasmuch as the bichloride of mer- 

 cury is extremely deadly to minute organisms, we have a right to con- 

 clude that life exists in the distilled water of laboratories, and that 

 such water contains also the aliments required for its development. 

 How can organic germs exist in water that has just passed through 

 the process of distillation ? Tyndall has shown the possibility of vapor 

 taking up germs as it passes through the air. M. Stas has proved that 

 distilled water may contain volatile organic matters which after a little 

 while become spontaneously fixed. We may, then, conclude that our 

 distilled water continued blue as long as the organic matters con- 

 tained in it continued volatile, but that it turned green as they be- 

 came fixed. 



It was necessary to obtain distilled water certainly free from or- 

 ganic matter. I did this by an adaptation of M. Stas's process of dis- 

 tilling spring-water over a mixture of manganate and permanganate 

 of potash into a cooling-vessel of platinum. The resultant water, 

 which met every test of its purity, when placed in the tubes, displayed 

 a color to which only the clearest blue of the sky, as seen from a 

 mountain-top on a perfect day, can be compared, the hue of which 

 was not changed after it had been left in the tubes for two weeks. 

 The color was evidently not due to reflection from minute particles, 

 for it was a color of transmission and had not a tinge of red in it ; 

 moreover, if it was due to the presence of foreign particles, all liquids 

 under the same conditions ought to have a bluish tinge. But amylic 

 alcohol, distilled under circumstances favorable to the absorption of 

 fine particles, was colorless, while acetic acid and ethylic alcohol were 

 yellow, when seen through a thickness of five metres ; and, though the 

 color was effaced as the thickness of the masses was reduced, no trace 

 of green or blue appeared in the liquids. It seemed proved to me 

 that water, as pure as we can get it, has a blue color, which proceeds, 

 not from reflection, but from an absorption of the yellow. 



To perfectly clear lime-water I added enough of a solution of car- 

 bonic anhydride to cause the formation of a barely visible precipitate, 

 and then poured the liquid into one of my tubes of observation. The 



