110 



CHEMISTRY. 



but M. Olszewski, in the course of his investiga- 

 tion of the absorption spectrum, has obtained a 

 sufficient quantity of the liquid 30 millimetres 

 thick, and has discovered that it possesses a blue 

 color like that of the sky. The direct experi- 

 ments on its absorption spectrum show that this 

 color is exactly what one would expect from its 

 nature. The author suggests that the blue color 

 of the sky may be simply due to the atmospheric 

 oxygen, which in gaseous layers of such extent 

 may exhibit the same color as when compressed 

 into a few centimetres of liquid. Apart from 

 the discussion of this debatable subject, the fact 

 is of interest to chemists that ordinary oxygen 

 and its condensation allotrope, ozone, when com- 

 pressed into the liquid state, are thus related as 

 to color, the former possessing a light-blue and 

 the latter a deep-blue tint. 



The results of an examination of the proper- 

 ties of liquid chlorine have been published by 

 Dr. Knietsch, of Ludwigshafen, in Liebig's "An- 

 nalen." The work included the determination of 

 the vapor density of liquid chlorine at tempera- 

 tures from 88 C. to + 146 C. (its critical 

 point), a complete examination of its behavior 

 near the critical point, and the determination of 

 its specific gravity and coefficient of expansion 

 for a range of temperature between 80 and 

 + 80. Liquid chlorine generally appears to 

 possess a yellow color. When, however, the 

 color of a long column is examined it is found to 

 have a distinctly orange tint The absorption 

 spectrum does not exhibit any characteristic 

 bands, but the blue and violet portions of the 

 spectrum are completely absorbed, and the trans- 

 mitted spectrum thus consists of the red, orange, 

 yellow, and green. The pressure is given for 

 every five degrees up to 40 C., and thence for 

 every ten degrees up to the critical point, 3'66 

 atmospheres at 0, 5'75 atmospheres at 15, 11-5 

 atmospheres at 40, and 93-5 atmospheres at 

 the critical point, 146. Some very interesting 

 results were obtained in determining the critical 

 point, the yellowish-green color of chlorine per- 

 haps assisting in rendering the appearance of 

 what has sometimes been termed the fourth state 

 of matter between the liquid and the gaseous 

 more distinct than usual. At 140 C. extremely- 

 small bubbles began to be developed through 

 the mass of the liquid, at 144 the hitherto sharp 

 meniscus began to disappear, and at 145 the 

 presence of a liquid was evident only by the 

 more intense yellow color and the higher re- 

 fractive power of the lower portion of the tube. 

 At 146 the contents of the tube were homogene- 

 ous throughout, the critical point being attained 

 and the liquid converted into a gas. On cool- 

 ing, the condensation always began below 146, 

 with the formation of a cloud and a fine rain of 

 minute yellow spheres of liquid chlorine. Liquid 

 chlorine is proved to be a very expansible sub- 

 stance. The coefficient of expansion at 80 C. is 

 already 0-00346, nearly equal to that of gaseous 

 chlorine, and is rapidly increasing, so that be- 

 fore the critical temperature of 146 is attained 

 the coefficient of expansion will be considerably 

 higher than that of the gas. 



The experiments of Prof. Vivian B. Lewes on 

 the spontaneous ignition of coal led him to re- 

 ject the explanation of Berzelius, which at- 

 tributes spontaneous ignition to the oxidation 



of pyrites contained in the coal. The heat 

 given off by the combustion of pyrites would 

 not be sufficient to raise the temperature of the 

 adjacent coal to the ignition point. The cause 

 of spontaneous ignition is to be found, on the 

 other hand, rather in its power especially when 

 finely divided of absorbing oxygen, which causes 

 the slow combustion of some of the hydrocarbon 

 constituents even at ordinary temperature. The 

 action may increase under favorable conditions 

 until ignition of the coal results. The risk is 

 greatest with large masses of coal and with the 

 ordinary air sxipply on board ships. The oxida- 

 tion increases rapidly with the ignition temper- 

 ature of the coal, so that coal fires are found to 

 occur most often on ships frequenting tropical 

 climates. It may be roughly estimated that the 

 absorbing power of a coal for oxygen is propor- 

 tional to its power of taking up moisture. Prof. 

 Bedsen said, in the discussion of Prof. Lewes's 

 paper, that in heating coal dust at various tem- 

 peratures up to 140 C. he had noticed that in 

 some cases combustible gases were given off by 

 the coal. 



Cumulative evidence has been gathered by Sir 

 Henry Roscoe and Mr. Scudder of the deposi- 

 tion of iron by burning water gas (which con- 

 sists of carbon monoxide and hydrogen) upon 

 the appurtenances of the burners and upon 

 whatever objects or substances it comes in con- 

 tact with. The amount of the deposit appears 

 to increase with the time the gas has been 

 stored in an iron cylinder, till at length the 

 gas becomes smoky on burning. Upon passing 

 some of this gas through a tube cooled with ice 

 a few drops of a turbid liquid were obtained, 

 which consisted chiefly of iron carbonyl. The 

 turbidity disappeared on the addition of hydro- 

 chloric acid. It is thus evident that iron car- 

 bonyl is produced in the cold by the action of 

 the carbon monoxide contained in the water gas 

 upon the iron of the containing cylinder A 

 similar deposit of metallic iron has been found 

 on the steatite burners from which ordinary coal 

 gas is burned, and this points to the existence of 

 iron carbonyl in our common illuminating gas. 

 This conclusion is strengthened by the fact 

 mentioned by Dr. Thome that coal gas which 

 has been compressed in iron cylinders and al- 

 lowed to stand for some time is unfit for lantern 

 projection on account of the deep stain of iron 

 that is found upon the lime cylinders., 



Dr. William Crookes described at the meeting 

 of the British Association his experiments on the 

 electrical evaporation of metals and alloys. Films 

 of gold, silver, and platinum were thus obtained 

 which could be peeled off from the glass on which 

 they were deposited and were homogeneous. 

 Different metals treated thus evaporate at dif- 

 ferent rates. A few, including aluminum and 

 magnesium, seem to be non-volatile. It is thus 

 possible, in the case of the gold alumimim alloy 

 discovered by Prof. Roberts- Austen, to separate 

 a large portion of the gold from the aluminum 

 by electrical evaporation. 



C. T. Heycock and E. H. Neville record the 

 results of experiments in the application of 

 Raoult's theorem that the solution of any sub- 

 stance in any solvent lowers the freezing point 

 of the solvent in a fixed degree to the dissolu- 

 tion of metals in metals. Making tin the 



