CHEMISTRY. 



115 



reaching this point of its development the concep- 

 tion of Prof. Mendeleef becomes essentially inju- 

 rious, ruder pretext of a law which has still to be 

 demonstrated, it forbids us to throw light on pure 

 matters of observation, and forces us to remain in 

 a visions circle from which there is no escape." The 

 author then undertakes to show that there is noth- 

 ing in the periodic classification which merits the 

 name of law or system. 



Chemical Physios. In M. Moissan's experi- 

 ments on the volatilization of refractory substances 

 in the electric furnace, the sublimates were con- 

 densed on the outside of a curved copper tube 

 placed 2 centimetres below the arc and just above 

 the substances under examination. A rapid cur- 

 rent of water was passed through the tube and 

 kept it cool during the experiments, which usually 

 lasted for about five minutes. The volatilized met- 

 als were copper, silver, aluminium, tin, gold, man- 

 ganese, iron, and uranium. Quantitative experi- 

 ments were not made in every case, but it appeared 

 that manganese was sublimed more rapidly than 

 the other metals, and that the rate of volatilization 

 of copper was about five times as rapid as that of 

 gold. The condensed metal was usually, or in great 

 part, in the form of little spheres. Silicon and 

 carbon were also volatilized and condensed on the 

 tube, though the amount collected of the last-named 

 element was very small, and lime, magnesia, zir- 

 conia, and silica were sublimed without difficulty. 

 The author draws the conclusion that the most 

 stable compounds hitherto known disappear in the 

 electric furnace, being either decomposed or vola- 

 tilized. Nothing resists these high temperatures 

 except the series of perfectly crystallized compounds 

 discovered by him, consisting of borides, silicides, 

 and carbides of the metals. He regards these sub- 

 stances as being probably among the original con- 

 stituents of the globe, and as still existing in some 

 of the stars. 



F. W. Clarke remarks that although many papers 

 have been written upon relations between boiling 

 point and critical temperature, the melting points of 

 substances seem to have been little considered. 

 Yet the subject is important. For any substance 

 the limits of the solid state are the absolute zero 

 and the melting point, while the extreme limits of 

 the liquid condition are the melting point and the 

 critical temperature. A comparison of the values, 

 therefore, will give for such substance the relative 

 thermometric lengths of the two states of matter, 

 and the results obtained, although empirical, have 

 very decided interest. The available data, how- 

 ever, are very meager, for many of the compounds 

 of which the critical temperature is known have 

 never had their melting points determined. Nine 

 substances nitrogen, carbonic oxide, argon, me- 

 thane, hydrochloric acid, hydrogen sulphide, am- 

 monia, benzene, and acetic acid give a ratio of 

 nearly 2 : or their absolute melting points are very 

 nearly, if not exactly, half of their critical tempera- 

 ture, and the thermometric lengths of their solid 

 and liquid states are approximately equal. This 

 simple ratio, however, is not general. In 30 

 substances examined no uniform rule has ap- 

 peared. There are nevertheless other regularities 

 apparent which connect certain allied substances 

 with one another. Thus 4 gaseous compounds of 

 nitrogen exhibit ratios of between T64 and !??. 

 and 5 aromatic bodies from 2'75 to 2'94. In 

 these appear an essential identity of ratio with 

 related constitution, which suggests that the method 

 of discussion applied to larger masses of data may 

 give information of considerable theoretical value. 

 For most of the other substances considered the 

 ratio ranges between 2'2 and 3. A few bodies only 

 give ratios higher than 3, and in these therefore 



the thermometric lengths of the solid and liquid 

 states are as 1 to 2 and more. 



A series of experiments on the transparency of 

 liquids is described by M. \V. Spring in the " Bulle- 

 tin " of the Royal Academy of Belgium. In a com- 

 parison of the colors of the alcohols with that of 

 water, none of the alcohols were colorless when the 

 thickness of fluid was 20 metres: methyl alcohol 

 appeared greenish blue, ethyl alcohol of a less warm 

 hue of the same color, and amyl alcohol greenish 

 yellow. The pure blue color observed in water be- 

 comes thus modified by the admixture of more and 

 more yellow as we pass from one term of the homo- 

 geneous series of compounds to the next. The ab- 

 sorbing powers of the various liquids for ordinary 

 light were also observed, and it was found that these 

 formed a descending scale, the simplest substance, 

 water, offering the greatest resistance to the passage 

 of light seen by the eye. M. Spring also discusses 

 the temperature at which the convection currents 

 begin to produce opacity in a column of water of 

 given length. When the length is 26 metres the 

 smallest difference of temperature that will suffice 

 is about 0'57 : , and is comparable with that which 

 doubtless exists in lakes and rivers. The author 

 concludes that we have here an explanation of the 

 varied colors often seen in water. They result 

 from differences of temperature caused by sunshine 

 on the one hand, and the cooling action of wind 

 blowing on the surface on the other hand. 



Subjecting the diamond to molecular bombard- 

 ment in a vacuum tube, Prof. Crookes has found 

 that it becomes discolored, and in the course of time 

 black on the surface. Some diamonds blacken in a 

 few minutes, while others require an hour or more 

 to discolor. The blackening is only superficial, and 

 although no ordinary means of cleaning will remove 

 it. it goes away when the stone is polished with 

 diamond powder. Ordinary oxidizing reagents 

 have little or no effect in restoring the color. The 

 author attributes the phenomenon to the conversion 

 of the outer layer of carbon molecules of the stone 

 into graphite. A diamond thus discolored was 

 digested in a mixture of potassium chlorate and 

 strong nitric acid at a temperature of about 50 C., 

 when after three days the superficial blackening 

 was entirely removed, and the gem was even more 

 brilliant than before. This was held to prove that 

 the blackening arose from the formation of graph- 

 ite. Microscopic examination under high powers 

 failed to show any alteration of the smooth crys- 

 talline surface either before or after the blackened 

 diamonds had been treated with the chemical re- 

 agents. 



During a preparation of mercurous nitrate by 

 the action of dilute nitric acid in the cold on mer- 

 cury. Dr. P. C. Ray, of the Presidency College, Cal- 

 cutta, observed that minute yellow crystals were 

 deposited which, upon examination, proved to be 

 mercurous nitrite. The analysis proved somewhat 

 difficult, as the substance decomposes in solution 

 into metallic mercury and mercuric nitrite. The 

 fact that this nitrite is stable in strongly acid solu- 

 tions is an additional proof, says " Nature." of the 

 views advanced' by Dr. Divers as to the "nitronic"' 

 constitution of the nitrites of copper, silver, mer- 

 cury, and bismuth. The stability of silver nitrite 

 toward nitric acid has already been noticed by 

 Ac-worth and Armstrong, and by Russell, and the 

 behavior of mercurous nitrite is closely analogous. 



In experimenting with deliquescent salts, H. 

 Wilson Hake found, several years ago. that such 

 bodies exercise a desiccating action on other deli- 

 quescent salts, indicating differences in the degree 

 of attraction for moisture. He has recently made 

 experiments for measuring, if possible, the relative 

 degree of deliquescence, or specific deliquescence, of 



