March 10, 1922] 



SCIENCE 



263 



stitutes for gi'ain alcohol, which would be un- 

 potable and free from internal revenue taxation 

 and prohibition regulations, are greatly desir- 

 able. Ordinary denatured alcohol, whUe use- 

 ful for some laboratory purposes, is not satis- 

 factory for most uses because of the character 

 of the denaturants; and the use of a special 

 denaturing formula is so involved in regula- 

 tions as to be almost impossible. 



A considerable series of experiments has 

 shown that isopropyl and chemically pure 

 methyl alcohols will fulfill practically any use 

 for which alcohol is needed in biological work. 

 It is indicated that inhalation of fumes of iso- 

 propyl alcohol does not have dangerous con- 

 sequences; certainly, in any properly ventilated 

 place the fumes would not be a danger. The 

 experience of those who work in factories 

 where methyl alcohol is produced, and who at 

 times inhale the fumes in large quantity, shows 

 that there is also little to be feared from its 

 use in the laboratory. Experiments along this 

 line are in progress. Probably niost persons 

 would prefer to use isopropyl alcohol for those 

 purposes which might cause considerable quan- 

 tities of the fumes to be inhaled. But both 

 alcohols can be used with perfect safety for 

 histological or other ordinary purposes. Out 

 of consideration for those who consider alcohol 

 a beverage all containers of both these alcohols 

 should display warning labels. 



The commercial grade of isopropyl alcohol 

 contains 91 to 92 per cent, of the alcohol, while 

 the similar grade of ethyl alcohol is 95 to 96 

 per cent. A purer grade of isopropyl alcohol, 

 98 to 99 per cent., can be supplied by the manu- 

 facturers, which can be made anhydrous by or- 

 dinary procedures. 



"Chemically pure" methyl alcohol is practi- 

 cally anhydrous, and being less hygroscopic 

 than ethyl alcohol is more useful and reliable 

 for such purposes as dehydrating tissues than 

 the anhydrous ("absolute") ethyl alcohol. As 

 it contains only a trace of acetone it is entire- 

 ly without the disagreeable odor of ordinarj' 

 wood alcohol. 



Both isopropyl and methyl alcohols have 

 been tested against ethyl alcohol in the prepa- 

 ration of reagents, and in histological work 



done with such reagents and stains, as well as 

 in the preservation of museum specimens. No 

 differences could be detected in favor of either 

 of them, except that the methyl alcohol proved 

 much more satisfactory as a dehydrating agent. 

 In addition to the advantage that methyl and 

 isopropyl alcohols have of being free from 

 vexatious regulations and the danger of ir- 

 regular use, they possess the additional merit 

 of competing in price with the tax-free com- 

 mercial ethyl alcohol. 



Lavteence E. Geiffin 

 Keed College 



IRIDESCENT CLOUDS 

 On the afternoon of January 2]., beginning 

 before four and lasting perhaps an hour, an 

 unusual set of iridescent cloud phenomena was 

 seen in the southwest. Low in the sky, part- 

 ly hiding the sun, were thick clouds edged 

 with brilliant gold, which remained practically 

 stationary. Higher up the sky was for the 

 most part clear, with occasional cirro-cumulus 

 clouds, many finger-shaped and pointing down- 

 ward to a point north of the sun. The edges 

 of these clouds were quite definite, and sur- 

 rounding the tips and sides were two or three 

 alternate narrow parallel bands of bright pink 

 and green, the outer band in most cases being 

 pink and the color extending at times 45° from 

 the sun. Some of the clouds showed flocculent 

 edges, giving an appearance of a colored fringe 

 and one cloud broke up entirely into horizon- 

 tal flecks and disappeared as it passed the 

 zenith. Besides these were detached clouds 

 which showed brilliant iridescent colors 

 throughout the whole. One thin flocculent cloud 

 showed small uniformly distributed flecks of 

 pink and green, a larger one showed four ir- 

 regular vertical bands of pink and green which 

 covered the whole cloud, several glowed with 

 lurid irregular patches of colors such as are 

 seen in a thin film of oil on water. In one case 

 a small spot of dark rose appeared against a 

 misty blue background, rapidly grew into a 

 pillar of vivid mottled colors, and then 

 stretched out toward the northeast to fonn a 

 white streamer all the way across the sky, its 

 western portion being bordered with the 

 characteristic pink and green bands. 



