September 25, 1890] 



NATURE 



531 



described only lo exist. Of the 14 possible triderivatives 13 are 

 known. Light has been thrown by these researches on the 

 mode of action of reagents upon naphthalene and other hydro- 

 carbons, and it appears that in all cases the initial action is the 

 same, the ultimate product depending on secondary causes, e.g., 

 in the case of benzene an ortho compound is always first ob- 

 tained, meta and para compounds being produced by secondary 

 causes. The influence of structure on the colouring properties 

 of naphthalene derivatives has also been studied in connection 

 with these researches. 



Prof. J. H. Van't Hoff read a paper on the behaviour of 

 copper potassium chloride and its aqueous solutions at different 

 temperatures. 



This compound, which is a blue salt, splits up on heating into 

 potassium chloride, water, and a brown double salt, according to 

 the following equation : CuCU 2KC1.2H20 = CuCUKCi + KCl + 

 2H2O. On cooling the reverse change takes place. The brown 

 salt can also be formed hv the action of cupric chloride on the 

 blue salt thus : CuCI., 2KCI aHoO + CuCla 2HoO=r2CuC!oKCl 

 + 4H2O. The changes of volume attending these transforma- 

 tions have been studied, also the solubility of the various con- 

 stituents of the system at different temperatures, and the vapour 

 pressure of their solutions, and interesting relations are shown 

 to exist between the values obtained in each case. 



Dr. Richardson read the Report of the Committee for the 

 investigation of the action of light on the hydracids of the 

 halogens in presence of oxygen. 



It has been found that the presence of ro per cent, hydro- 

 chloric acid prevents all decomposition of chlorine water, even 

 after long exposure to sunshine. 



Aqueous solutions of pure bromine and iodine have been ex- 

 posed to sunlight for a period of fourteen months. It was found 

 that, in a dilute solution of bromine water (o'l6 per cent. Br.), 

 as much as 57 per cent, of the total bromine is converted into 

 hydrogen bromide ; in a saturated solution the minimum amount 

 of decomposition occurs, again increasing with further additions 

 of bromine. With iodine water under an atmosphere of carbon 

 dioxide, 8-3 per cent, of the total iodine in the solution was 

 converted into hydrogen iodide. Under an atmosphere of air 

 I4"2 per cent, of the total iodine was converted. Further ex- 

 periments have bsen made on the oxidation of gaseous hydrogen 

 bromide in sunlight. The presence of free bromine exercises a 

 retarding influence on the decomposition. 



The influence of temperature on the oxidation of hydrogen 

 chloride and bromide has been studied. Rise of temperature 

 appears to retard oxidation in the first case and accelerate it in 

 the second. 



Profs. Liveing and Dewar gave a paper on some experiments 

 on tlie explosion of gases under high pressure. It was found 

 that with increase of pressure the luminosity of the flame steadily 

 increased. When hydrogen was exploded with excess of oxygen, 

 it was found that large quantities of nitrogen peroxide were 

 formed from the nitrogen present as impurity in the oxygen. 

 The water formed contained 3 per cent, of nitric acid. With 

 excess of hydrogen small quantities of ammonia were formed. 

 It was found that, in an atmosphere of carbon dioxide, it was 

 very difficult to maintain the oxy-hydrogen flame if the pressure 

 exceeded two atmospheres. Experiments were also made with 

 ethylene and cyanogen exploded with oxygen. 



Prof. H, B. Dixon and J. A. Harker gave a paper on the 

 rates of explosion of hydrogen and chlorine in the dry and wet 

 Slates. They showed that there was no great difference in the 

 rate, such as they had previously found with carbonic oxide and 

 oxygen mixtures, thus showing that, in the case of hydrogen 

 and chlorine, the aqueous vapour simply acts like any other 

 inert gas, making the rate a little slower. 



Dr. G. S. Turpin read a paper on the ignition of explosive 

 gaseous mixtures. The author has commenced a thorough in- 

 vestigation of the conditions affecting the ignition of explosive 

 mixtures of gases, and the present paper gives an account of the 

 results obtained in a series of experiments on the temperatures of 

 ignition of various mixtures of CS^ vapour with oxygen and other 

 gases. The method used is a modification of Mallard and 

 Chatelier's second method, in which the gases are introduced 

 into a heated and exhausted bulb. The existence of a dis- 

 continuity between gradual combustion and ignition proper is 

 found to exist in some cases, while in others there is a perfect 

 gradation from slow combination, attended by a faint glow, to 

 mstantaneous combination, attended by a bright flame. The 

 effect of change of pressure on the ignition was examined and 

 found to be somewhat complex. 



NO. ICQ I, VOL. 42] 



The Report of the Committee on the properties of solutions 

 was read by Dr. Nicol. The experiments have now been com- 

 pleted on the solubility of a salt in a solution of another salt, of 

 known strength. In general a salt is less soluble in a salt solu- 

 tion than in pure water. An exception is the case of the solubility 

 of KNO3 in solution of NaNOj. 



A joint discussion with Section A on the nature of solution 

 and its connection with osmotic pressure was opened by Prof. 

 Pickering, in a paper on the present position of the hydrate 

 theory of solution. The supporters of the hydrate theory claim 

 that the curved figures, representing the properties of solutions 

 of various strengths, show sudden changes of curvature at certaitt 

 points, which are the same whatever be the property examined, 

 which correspond to the composition of definite hydrates, and 

 which, therefore, can only be explained by the presence of these 

 hydrates in the solutions ; while the supporters of the physical 

 theory, now identified with the supporters of the osmotic pressure 

 theory, claim to have shown that, with weak solutions at any 

 rate, the dissolved substance obeys all the laws which are 

 applicable to gases, and that, therefore, its molecules must be 

 uninfluenced by, and uncombined with, those of the solvent. 



With regard to the lowering of the freezing-point of a solvent, 

 the following questions were proposed :— 



(1) Is the molecular depression (i.e. that produced as calculated 

 for one molecule dissolved in loo molecules) constant, independent 

 of the nature of the solvent? 



(2) Is it independent of the strength of the solution, so long 

 as this strength does not exceed' the limits (gas strength) above 

 mentioned ? (Boyle's law). 



(3) Is it independent of the nature of the dissolved sub- 

 stance ? (Avogadro's law). 



Evidence was adduced involving a negative answer to each of 

 these questions. 



Objection was taken to the theory of dissociation into ions, 

 on the grounds of its irreconcilability with our ideas of the relative 

 stability of various bodies, and with the principle of conservation 

 of energy. 



A letter was afterwards read from Prof. Arrhenius in which it 

 was shown that both the osmotic pressure and the electrical 

 dissociation theories must be taken into account in drawing 

 conclusions from observed numbers. 



Prof. Armstrong remarked that, according to the electrical 

 dissociation theory, hydrochloric acid and water must be re- 

 garded as entirely different substances, whereas in their chemical 

 relations they are very nearly allied. 



Prof. Fitzgerald, Prof. Ostwald, and Prof. Lodge all spoke 

 to the effect that Ostwald's experiment, on the decomposing 

 effect of a charged body on a salt solution, does not involve a 

 contradiction of the principle of the conservation of energy. 



P. J. Hartog and J. A. Harker described a convenient 

 form of apparatus for determining freezing-points, and for 

 performing reactions in the cold. Adopting a proposal of 

 Raoult, the evaporation of a volatile liquid is used to produce 

 low temperatures. 



A paper was given by A. G. Green, C. F. Cross, and E. J. 

 Bevan, on a method of photographic dyeing and printing. It 

 was observed that the diazo-compound of primuline was decom- 

 posed by light, thereby losing its property of combining with 

 phenols and amines. If a material, dyed with diazotized primuline, 

 be exposed to light under a design, those parts which are acted 

 upon by light will be decomposed, whilst the parts protected 

 from the light will remain unaltered, and consequently on 

 subsequent development with a phenol or amine, will produce 

 colours, whilst the decomposed portions will not. 



Prof. Thorpe gave a demonstration of some of the most 

 striking properties of phosphorous oxide. He believes that the 

 physiological effects usually ascribed to phosphorus are due in 

 reality to this oxide. 



Prof. R. Meldola read a paper on diazo-amido;compounds, 

 a study in chemical isomerism. The paper dealt largely with 

 heterogeneous diazo -amides, which the author believes have the 

 general constitutional formula — 



X— N— N— NR'— Y 



I I 

 Y— N— N— NR'— X 



thus being derivatives of a hypothetical tetraimine — 



HN— NH 



I I ■ 

 HN— NH 



