General and physical chemistry

1905 Journal of the Chemical Society Abstracts  
Chemistry of Phosphorescing Sulphides of the Alkaline Earths. PERCY WAENTIG (Zeit. physikal. Chem., 1905, 51, 435-472. Compare Abstr., 1903).--The author's experiments confirm the view that the marked phosphorescence exhibited by the sulphides of the alkaline earths is conditioned by the presence in solid solution of a small quantity of certain heavy metale. A purified sample of strontium sulphide has been obtained exhibiting only a very faint blue phosphorescence, and this residual
more » ... nce was traced to the presence of iron. Platinum, even in traces, also appears to have the power of causing phosphorescence in the sulphides of the alkaline earths. The intensity of the phosphorescence increases with the concentration of heavy metal present so long as the latter is dissolved to a homogeneous solid solution. The solubility of these heavy metals increases with rising temperature, and is very small at the ordinary tempernt ure ; all phosphorescing sulphides, therefore, which have been obtained by heating an alkaline earth carbonate and sulphur with the nitrate or sulphate of the heavy metal are to be regarded a t the ordinary temperature a s supersaturated solutions. Hence inany factors are to be considered in the preparation of a highly phosphorescent sulphide, such as the temperature a t which the sulphide is to be prepared, the duration of the heating, and the rate of cooling, Allowing for the influence of these various factors, the author has prepitred sulphides, the phosphorescent efficiency of which is greater than t h a t of the products obtained by the usual methods. The presence of a small quantity of a fusible salt is favourable for the production of a highly phosphorescent sulphide, because (1) it promotes the solution of the heavy metal in the sulphide, (2) i t hinders the separation of the heavy metal during the process of cooling. When the sulphides of the alkaline earths are ground in a mortar, they become coloured and lose, to a large extent a t least, their phosphorescent power. The colour assumed varies with the sulphide used, and depends neither on the heavy metal present nor on the original phosphorescence colour. The coloured powder is unstable compared with the original white phosphorescent material. The change can be effected in either direction a t one and the same temperature. Intermittent illumination over a period of several months does not apparently lead to any diminution of phosphorescent power : so far, therefore, there is no indication that a chemical change is involved. J. C. Y. The Light emitted by Crystals of Arsenious Oxide. DESIRB GERNEZ (Conzpt. rend., 1905, 140, 1134--1136).-The luminous effect which accompanies the formation of octahedral crystals of arsenious oxide from hydrochloric acid solutions of the vitreous variety is due t o the rupture of the crystals induced by contact with one another, and P( 1 1 O0/lo) = 54.47 + 0.1 97t. The double salt, CdBr2,RbBr, forms anhydrous crystals and has P( 10'7'/Oo) = 35.34 + 0.393t. Solubility determinations with rubidium bromide give the value P(114"/0*5") = 48.63 + 0.1751t. The following values were calculated from solubility determinations by other authors : for KBr, P(lOOo/Oo) = 36.192 + 0.1543t ; for NH,Br, I'(100'/10") = 38.958 + 0*1$6St ; for CdBr2, (36O/Oo) = 37.803 + 0.6319t. P(100°/360) = 59.583 + 0.0183t ; These results agree with the rule that the value dP/dt is greater for double salts than for their constituents. The double salt, CdBr2,4NH,Br, formed from a solution of its components containing excess of cadmium bromide, separates in hexagonal plates [a : c = 1 : 0.62691 ; when shaken with water at from 0.8' to 123*5", i t partly decomposes, the solution containing a n excess of cadmium bromide, the solid, the unchanged salt and ammonium bromide; the transformation point is passed by 160". The double salt, CdBr2,4KBr (Eder, Zoc. cit. ; Hauer, Zoc. cit.), cannot be formed from a solution of its components at temperatures up ta 160". The double salt, CdBr2,4RbBr, crgstallises in hexagonal plates [ch : c = 1 : 0.62311 ; the salt is isomorphous with the corresponding ammonium salt ; the solubility determinations give the value P(llS0/O0) = 50.88 + 0.2637t. With alkali iodides, cadmium iodide forms the two series of salts, CdI"M'I and Cd12,2 M'I,2H2O ; the latter forms large, transparent, hygroscopic cry s t a1 s. It has been shown t h a t double salts which, when shaken with water, form incongruent saturated solutions containing a n excess of one component are not decomposed by a solution of that component. It is POW found that the excess of the one component necessary to form the double salt may be replaced by other substances having the same anion. Thus the dissociation of CdCI2,4KC1 by water is diminished by the presence of hydrochloric acid or lithium, calcium or magnesium chloride, and when these salts are present in certain concentrations no dissociation of the double salt takes place; the effective molecular percentage concentration at 16" for CaCI, is 0.1887, for LiCl 0.4483, for HC1 0.8828. Similarly with the double salt, CdC1"4RbCl, the incongruent saturated solution of which contains an excess of 12.83 mols. of RbCl over each mol. CdC12,4RbC1, the minimum effective molecular percentage concentration for CaCl, is over 4-59, for LiCl over 19.4, for HC1 over 29.8. The double salt, CdCI2,4NH,Cl, is obtained from solutions of its components containing hydrochloric acid, lithium, calcium, or magnesium chloride. The dissociation of the double salt, CdBr2,4NH,Br, which forms a saturated solution containing a n excess of cadmium bromide, is pot affected by the presence of hydrobromic acid or lithium, calcium, magnesium, nickel, or cobalt bromides, but the pure double salt is obtained by mixing solutions of its components and zinc bromide. The double salt, U0"S0"2K,S0"2H20, is completely dissociated on recrystallisation from dilute sulphuric acid, the solution depositing UO,SO" K,SO,. G. Y. Mixed Crystals in Systems of Three Substances. 11. FRANS A. H. SCHREINEMAKERS (Zeit. physikal. Chem., 1905, 51, 547-576. Compare .this vol., ii, 154).-A theoretical paper. J. C. P. A Rule in Chemical Dynamics. JOH. PLOTNIKOFF (Zeit. physikccl. Chem., 1905,51, 603 -608).-The curves obtained by plotting reaction velocity-coefficients against temperature are similar to those representing the course of the reaction, The latter are logarithmic curves,
doi:10.1039/ca9058805365 fatcat:aflngf2isbgvrezonrkxzlrfrm