V 



July 2, 1891] 



NATURE 



215 



small pieces, as it was brittle and porous. Weighing the brush 

 that had formed, the negative pole gave the following results : — 



Grains. 



... io'i940 

 ... 81570 



Weight of platinum before experiment 

 ,, ,, after experiment ., 



Loss by volatilization in 25 hours 



2-0370 



Another experiment was made similar to that with gold and 

 platinum, but using silver as the negative pole, the pure metal 

 being formed into a brush of fine wires. Less gas was occluded 

 (luring the progress of this experiment than in the case of 

 |)latinuni. The silver behaved the same as gold, the metal 

 deposited freely, and the vacuum was easily kept at a dark space 

 of 6 mm. by the very occasional admission of a trace of air. 

 In 20 hours nearly 3 grs. of silver were volatilized. The deposit 

 of silver was detached without difficulty from the glass in the 

 form of bright foil. 



Chemical Society, June 4. —Mr. W. Crookes, F.R.S., Vice- 

 President, in the chair. — The following papers were read ; — The 

 molecular refraction and dispersion of various substances in solu- 

 tion, by Dr. J. H. Gladstone, F.R.S. The paper is a continuation 

 of that laid before the Society in March last, and deals with solid 

 and gaseous substances that have been dissolved in water and 

 other liquids for examination. The results are given in several 

 ibles. In the case of organic compounds, the theoretical and 

 \perimental numbers are frequently in close agreement, 

 i lydrogen chloride, bromide, and iodide give figures for the 

 molecular refraction and dispersion much higher than the sum 

 of the hydrogen and halogen as determined from the paraffin 

 compounds, and the values rise as the dilution becomes greater, 

 Selenious and selenic acids afford optical values much less than 

 what would be expected from the known values of their con- 

 stituents. Metaphosphoric acid does the same. The data re- 

 lating to solutions of salts and alkalies will afford material for a 

 revision of the refraction equivalents of the different metals, and 

 of the electro-negative elements with which they are combined. 

 Vmmonia, in contrast with the hydrides of chlorine, bromine, 

 id iodine, appears to be uniform in its optical properties, 

 whatever the strength of the solution. The refraction equiva- 

 lents of cerium, didymium, and lanthanum were found about 

 1 2 '4, 1 6 '4, and 15 "5 respectively. The molecular refraction for 

 ' no., in its salts dissolved in water comes out at about l8"3, that 

 )r BrOj at 24 9, and for IO3 at 33-8. — The nature of solutions 

 I- elucidated by a study of the densities, heat of dissolution, 

 uul freezing-points of solutions of calcium chloride, by S. U. 

 Pickering. The curves representing these properties were exa- 

 mined in the same way as those for sulphuric acid, and similar 

 conclusions are drawn — namely, that changes of curvature, 

 which occur at certain points which are the same whatever 

 property is examined represent the existence of hydrates in 

 olution. The simplest hydrates indicated consist of CaClj with 

 ., 7, and SHjO ; more complex hydrates also exist, as in the 

 ase of sulphuric acid. — Note on a recent criticism by Mr. 

 ~>ydney Lupton of the conclusions drawn frotfi a study of various 

 properties of sulphuric acid solutions, by S. U. Pickering. Mr. 

 Lupton {Phil. Mag., xxxi. 418) applies a single parabolic equa- 

 tion to a portion of one of the author's sulphuric acid density 

 curves, where a change of curvature was supposed to exist, and 

 shows that it represents the results accurately if the experimental 

 error is of a certain magnitude. This magnitude is between 

 1000 and 10,000 per cent, greater than the ascertained magni- 

 tude, and the equation represents all errors of like signs as 

 i^rouped together. Such a representation cannot disprove the 

 existence of the particular change of curvature under examina- 

 tion, still less that of the loi others examined by the author. 

 The hydrate on which Mr. Lupton considers that his investiga- 

 tion throws " very grave suspicion " happens to be the one which 

 the author has isolated in the crystalline condition. In the dis- 

 cussion which followed. Prof. Ramsay doubted the validity of Mr. 

 Pickering's methods of differentiating his curves. His own experi- 

 ence was that it was impossible to obtain results nearer than 2 or 3 

 per cent, to the truth. Dr. Armstrong said that he was prepared 

 to believe in the existence of hydrates in solution, but could not 

 imagine that the 102 breaks in the sulphuric acid curves, for 

 example, could be interpreted as evidence of as many distinct 

 hydrates. He was inclined to think that the breaks might be 

 due to change both in the complex water molecules and the 

 sulphuric acid. He was inclined to believe that the hydrate, to 

 which Mr. Lupton's conclusions related, did not begin to form 



in solution until the temperature sank to within a few degrees of 

 its point of fusion. Dr. Morley said that a break in the curve 

 should indicate that some new hydrate had just begun to form, 

 but need not show what that hydrate was. Thus, a liquid of 

 the composition CaCl28H20 might be expected to contain, 

 besides the hydrate CaCl28H20, also higher and lower hydrates, 

 such as CaCUgHoO and CaCl27H20. Prof. Riicker said that, 

 in reality, Mr. Pickering's results were obtained, not by calcula- 

 tion, but by a method of observation and experiment applied to 

 curves, which themselves represented the results of other experi- 

 ments. It was admitted that the curves had to be specially 

 drawn, and the scale of the co-ordinates carefully chosen, if the 

 results were to be satisfactory, and probably the conclusions 



■ arrived at depended in a large measure on the details of this 

 preliminary adjustment. In the case of the more striking 

 changes in direction and curvature which were clearly visible in the 



j original curve, the various differential curves did not add much 



■ to the information it supplied. He thought that the evidence 

 afforded by these secondary curves of changes of curvature, not 



I otherwise detected, was of the most untrustworthy character. 

 I Mr. Pickering said that Mr. Lupton's equation represented the 

 rate of change of the densities as a straight line, while the figure 

 I which the actually observed rate of change formed was as dif- 

 I ferent from a straight line as possible. The figures here referred 

 [ to were the first differential figures (rate of change) deduced 

 ! directly from the determinations themselves ; the question of 

 the accuracy attainable in differentiating a graph, raised by 

 Prof. Ramsay, did not apply. He thought that Prof. Arm- 

 strong was somewhat rash in holding that a particular 

 hydrate did not exist in solution at moderately high tem- 

 peratures, because he had recognized it at low temperatures 

 only, especially as he (the speaker) had been led to search 

 for it, and finally to isolate it from results obtained at 

 high temperatures. The multiplicity and complexity of the 

 hydrates indicated must endanger the acceptance of his conclu- 

 sions amongst chemists ; and he was perfectly ready to accept 

 any other explanation of the changes with weak solutions. — 

 Ethylic oo'-dimethyl-ao'-diacetylpimelate and its decomposi- 

 tion-products, by Dr. F. S. Kipping, and J. E. Mackenzie. 

 This paper contains an account of the preparation and pro- 

 perties of the following compounds : ethylic ao'-dimethyl- 

 aa' -diacetylpimelate, ao'- dimethyl -oa'-diacetylpentane, aa'- 

 dimethyl-a-acetylcaproic acid, aa'-dimethylpimelic acid, and 

 ethylic-oo'-dimethylpimelate. — Volatile platinum compounds, by 

 W. Pullinger. The author has studied the volatile compounds 

 of platinum with chlorine and carbon monoxide described by 

 Schiitzenberger. He describes their behaviour when heated in 

 various gases ; as they do not completely volatilize, a deter- 

 mination of the vapour-density was not possible. He describes 

 a non-volatile compound of the formula PiCla-CoOo, and has 

 also prepared the compound PtBrnCO. Directions are given 

 for the preparation of platinic bromide and iodide, from which 

 it appears that spongy platinum readily dissolves in hot solu- 

 tions of bromine in hydrobromic acid or of iodine in hydriodic 

 acid. 



Mineralogical Society, June 16. — R. H. Scott, F.R.S. , 

 President, in the chair. — The following papers were read : — On 

 the occurrence of sapphire in Scotland, by Prof. M. Forster- 

 Heddle. — On the optical properties of gyrolite, by Prof. M. 

 Forster-Heddle. — On Fresnel's wave-surface, by L. Fletcher, 

 F.R.S. 



Linnean Society, June 18. — Prof. Stewart, President, in 

 the chair. — Mr. W. H. Beeby exhibited specimens of Hieracium 

 protractum and other plants collected in Shetland. — Mr. Stuart 

 Samuel exhibited a dwarf specimen of Acer palniahim, and 

 made some remarks on the dwarf trees artificially produced by 

 the Japanese. — Mr. R. V. Sherring showed some cases of dried 

 Bananas, and described a new method of preservation adopted 

 in Jamaica to save waste of small parcels of fruit which would 

 be otherwise unsaleable. — Mr. A. W. Bennett exhibited and 

 made remarks upon a specimen of Selagindla lepidophylla, 

 which was found to possess remarkable vitality, and upon proper 

 treatment to resume its normal appearance after having been 

 gathered some months. — Dr. R. A, Prior exhibited samples of 

 the Spiked Star of Bethlehem {Ornithogaltivi pyienaicum),z.m\ 

 stated that, although described in British floras as a rare plant, it 

 is so abundant on the hill pastures around Bath that it is brought 

 to the market there in large quantities under the name of French 

 asparagus, and sold for a penny a bunch. — Mr. R. A. Rolfe 



NO. TT3I, VOL. 44] 



