542 



NATURE 



{Oct. 6, 1881 



been previously computed. Expressed in the form usual in our 

 catalogues ilie elements are : — Perihelion passage, September 

 I5'0i G.M.T. ; longitude of perihelion, 250° 4'; longitude of 

 ascending nrde, 260° 43'; inclination, 72° 33' ; log. perihelion 

 distance, 970535 ; motion, retrograde. The intensity of light 

 is diminishing. 



Minima of Algol. — The under-mentioned Greenwich times 

 of minima of this v.iriable are from Prof. Winnecke's ephemeris, 

 in the computation of \\hich coiTCction depending upon recent 

 observatioiis has been applied : — 



Oct. 



Nov. I 

 4 

 7 

 21 

 24 

 27 

 30 



Dec. II 

 14 

 17 



17 48 



14 37 



II 26 



8 14 



S 3 



There would appear to have been pertm'bations in the period 

 during the last few years which are not reached even by Prof. 

 Schonfeld's formula involving two inequalities, which would 

 make the above times about thirty-live minutes later. 



A Probably Variable Star. — Prof. Pickering notifies his 

 observation of a red star, with banded spectrum, the place of 

 which on September 14 w-as in R.A. i6h. 31m. 32s. ; Decl. 

 + 72° 32'. On September 17 its magnitude was S'6. It is not 

 found in the " Durchmusterung,"nor in Federenko, Schwerd,"or 

 other circumpolar catalogue. Its variability is therefore suggested. 



Ceraski's Variable, U Cephei. — Mr. Knott informs us 

 that he obtained a good observation of the minimum of Ceraski's 

 variable of short period on the night of October 2 ; lime of 

 min. iih. 47m. G.M.T., mag. 9'2. Prof. Schmidt's ephemeris 

 in Astron. Nach., No. 23S2, has ilh. 37'Sm. The star did not 

 fall quite so low, as in the minima which Mr. Knott observed in 

 March, April, and May last. 



[Erratum.— In last week's "Astronomical Column" (p. 520), 

 for "add/" read "add P."] 



CHEMICAL NOTES 



MM. Schutzenberger AND COLSON describe (Compt. rend.) 

 several new compounds of silicon. When crystalline silicon is 

 strongly heated in a current of cai'bon dioxide the compound 

 (SiCO).v is produced When nitrogen is passed over a hot 

 mixture of silicon and carbon (SijC^N)^- is formed. The authors 

 regard these compounds as the oxide and nitride respectively of 

 the radicle carbo-silicon (S,i^C^)x. The nitride of silicon (SijNg), 

 is also described : it is obtained by the direct union of nitrogen 

 and silicon. 



It is well known that certain metallic chlorides, e.g. sodium 

 chloride, ai'e precipitated from aqueous solution by hydrochloric 

 acid ; attention has been drawn in these Notes to recent work of 

 Ditte and others on this subject. M. Sabatier describes several 

 hydrates of ferrous and ferric chloride (Compt. rend.) produced 

 by this general reaction. 



Many years ago Graham drew attention to the change in pro- 

 perties produced in certain oxides by the action of heat, e.g. 

 fen-ic oxide is soluble in hydrochloric acid, but when strongly 

 heated it becomes almost insoluble. This "department of 

 corpuscular philosophy " — to use Graham's phrase — has not been 

 much studied. The experiments detailed in Archiv Nierlandhy 

 M. van Benmelen form an interesting conti'ibution bearing on this 

 subject. It is shown that the amount of water of hydration taken 

 up by the oxides of tin, silicon, and mmganese at the moment 

 of the formation and precipitation of the hydrates of these oxides 

 from aqueous solutions, is dependent on the molecular state, i.e. 

 on the as yet unknown conditions of molecular equilibrium, of 

 the solid hydrates. The molecular state being the same, the 

 amount of water of hydration rises with temperature and humi- 

 dity of the sun-ounding air ; to each temperature and degree of 

 humidity coiTesponds a certain equilibrium of oxide and water ; 

 the relations between the weights of the oxide and water are 

 generally too complex for expression by a simple formula. From 

 an examination of the phenomena attending the action of the 

 amorphous hydrated di-oxides of the above-named elements on 

 acids, alkalis, and salts, M. van Bemmelen concludes that weak 

 double compour.ds are produced, but that these are very easily 

 dis.sociated ; the amount of dissociation varying \a ith the chemi 



cal nature and the mass of the reacting substances, and with tic 

 temperature. In most ca.'es stable compounds are pioduc;d 

 simultaneously with thee series of unstable and Largely-disso- 

 ciated compounds. The formation and dissociation of su;h 

 unstable compounds depend also on the conditions of molecular 

 stability of the hydrated oxides themselves. By arranging thtse 

 conditions so as to insure considerable molecular stability — e.g. by 

 heating the hydrates — the power of forming the unstable com- 

 pounds is much diminished. That a force of the same nature as 

 chemical affinity is concerned in the formation of some of these 

 weak compounds is shown by the decomposing action exerted by 

 hydrated Mn02 on the stable compounds K2SO4, Ktl, and 

 KNO3, compounds which do not show signs of dissociation in 

 aqueous solution. M. v.an Bemmelen would thus extend the 

 sphere of chemical phenomena, and would see no sharp division 

 line between the actions of the so-called physical forces — adhe- 

 sion, absorption, &c. — and the force of chemical affinity. 



An ingenious method for determining the total solid matter in 

 solution in different waters is described in Chcm. Soc. youmal 

 by Dr. Mills. The method is based on the fact that if a small 

 glass bead \\ ith an attached w'eight is allowed to ascend in a saline 

 solution of known strength, it will rise more slowly, the greater 

 the amount of solvent present. Experiments are given showing 

 that the rate of ascent is also dependent on the nature of the 

 soluble matter, i.e. on the viscosity of the solution. For detect- 

 ing variations in the solids in the same water, for prejiaring 

 standard solutions, &c., the bulb method is likely to be useful. 

 Experiments detailed in the same paper lead Mills to regard the 

 specific gravity of a potable water as a direct indication of the 

 quantity of total solids in solution. 



Analyses of the mud deposited round the Buxton thermal 

 spring, by T. C. Thresh {Chcm. Soc. ynirti.], show that when 

 dried at 120° this mud contains about 71 per cent. Mn304, with 

 oxides of Pb, Cu, Fe, Al, Zn, Ea, Sr, Mg, and Mo, and closely 

 agrees in composition with many specimens of "wad" or "bog 

 manganese." Analyses of the gas evolved at the spring and of 

 the gases disolved in the water closely confirm those made by 

 Playfair in 1852 : the gas evolved at the spring consists of about 

 99 per cent, nitrogen and i per cent. CO2, that di- solved in the 

 water of about 60 percent. N and 40 per cent. CO.^. The water 

 in the laihs contains as much gas as could be forced into water 

 at a pressure of 1*64 atmospheres, 



A LONG and important paper by W. H. Perkin, on " Isimeric 

 Acids obtained from Couniarin and the Ethers of Hydride of 

 Salicyl," appears in the same number (August) of the Chem, Soc. 

 Joutn. Perkin has obtained two series of compounds, differing 

 in properties, but generally convertible, one into the other, by 

 the action of heat. He thinks that the ordinary theory of iso- 

 merism, according to which this phenomenon is traceable to the 

 occupation of different relative positions by the atoms in two mole- 

 cules, fails to explain the cases of isomerism now described by him. 

 He favours the view that the atoms in the molecules of any | air 01 

 the newly dejcribed comp' unds occupy the same relative posi- 

 tions, but are at different absolute distances from each other. It 

 is, however, to be remembered that the present theoi-y of iso- 

 n erism is applicable only to gaseous molecules ; the molecular 

 phenomena of liquid and solid bodies are too complex to find, 

 as yet, any general explanation. Perkin's new compounds seem 

 to belong to this rapidly-increasing group of " physical iso- 

 merides," i.e. to liquid or solid bodies who e chemical properties 

 are to be traced to the binding together of molecular groups, the 

 individual members of which occupy rekatively different positions, 

 and which groups react as chemical units. The facts concerning 

 molecular volumes of melameric compounds are also, on the 

 whole, oppo-ed to that theory of isomerism favoured by Perkin 

 in his important | aper. 



A SERIES of papers on the photo-chemistry of silver bromide 

 by Herr Eder has appeared in C/iemisches Centrcilblatt. It is 

 shown that silver bromide prepared with an excess of silver 

 nitrate is much more sensitive towards light than when prepared 

 with excess of potassium bromit'c, provided the silver bromide 

 is disseminated through an indifferent substance, e.g. collodion 

 pyroxylene. When disseminated thi'ough an easily oxidisable 

 substance, e.g. gelatin or gum, silver bromide prepared with a 

 slight excess of soluble bromide is from four to six times more 

 sensitive than when disseminated through indifferent collodion 

 with excess of silver nitrate. An emulsion of silver bromide in 

 gelatin with a slight excess of the soluble bromide after several 

 days digestion at 30°-5o'' becomes much more sensitive than any 



