Dec. 30, 1880] 



NA TURE 



207 



ence. Hence so far as the paucity of data in 1873 enabled any 

 judgment to be formed, the preference apjieared to belong to tlie 

 revolution in 6'977 years. On this supposition there would be 

 a very near approach to the orbit of Jupiter near the ascendinij 

 node, which would render possible an amount of perturbation 

 at some past time, that might have fixed the comet in an orbit of 

 such limited dimensions. 



If the comet were really revolving in an elliptical orbit with 

 this period of revolution, neglecting perturbations, which might 

 however l)e sensible since 1873, it would be again due at peri- 

 helion about Nov. mber 24 in the present year, in which case its 

 track in the heavens would not be very different fr.jm that 

 followed in 1S73. We are not aware if any search has been 

 made for the comet. It would have been possible to have 

 decided in 1873 'f ^ short period were admissible could observa- 

 tions have been obtained in the southern hemisphere: this was 

 not done, and the identity of the comets of 1818 and 1873 

 remains therefore open to conjecture ; but it must be borne in 

 mind that the data in the former year are in a high degree 

 uncertain. 



Pechule's COiMET. — Elements computed by the discoverer 

 from observations at Copenhagen on December 16, 17, and 20, 

 have a general. resemblance to those of the comet of 1807, so 

 elaborately discussed by Bessel, but after his resulting period of 

 many centuries, and considering the position of the orbit in the 

 system, there can be of course no que-tion of identity of these 

 bodies. At Greenwich noon on January I the comet's position 

 will be, by Pechule's elements, in K.A. 2oh. I '9m., N.P.D. 

 70° 24', and on January 5 in K.A. 20I1. ig'6m., N.P.D. 68° 30'. 



CHEMICAL NOTES 



MM. Hautefeuille and Chappuis, in continuing their 

 investigation of the conditions under which oxygen is trans- 

 formed into ozone, have shown in Cotnpt. rend, that the 

 character of the electric discharge to which the oxygen is 

 subjected largely influences the quantity of ozone produced. If 

 the discharge assume the character of a luminous shower the 

 maximum amount of ozone is produced, the temperature of such 

 a discharge being lower than that of the ordinary effiuve. The 

 production of this special form of discharge is ensured by mixing 

 with the oxygen a smiU quantity of a foreign gas whose physical 

 properties are dissimilar from those of oxygen ; of the gases 

 experimented with silicon fluoride has given the best resUits. 

 If nitrogen be the foreign gas the transformation into ozone is 

 greater than when pure oxygen is employed, but the discharge is 

 not altogether luiiiin jus. Hydrogen is more effective than 

 nitrogen. The jiresence of carbon dio.xide also insures a large 

 amount of ozonation. In their earlier experiments on the lique- 

 faction of ozone the authors only succeeded in obtaining a mist in 

 the Cailletet tube when the pressure was suddenly withdrawn. 

 They now find that if a mixture of carbon dioxide and oxygen 

 which has been ozonised at a low temperature be submitted to 

 the action of the silent discharge at — 23", and be slightly com- 

 pressed, the gas acquires a deep blue colour, and after a time a 

 blue liquid is produced. At — 88" the liquid is very dark blue. 

 When carbon dioxide is decomposed by the electric spark at 

 - 23° a blue gas is produced, and at a certain ])ressure (exact 

 pressure is not mentioned) the undecomposed carbon dioxide 

 condenses to a blue coloured liquid. By this experiment the 

 authors think they have proved that ozone is one of the products 

 of the decomposition, by the spark, of carbon dioxide. 



The heat of formation of benzene has recently been measured 

 by Thomsen (Berlimr Berichte) and by lierthelot (CoiiipL rend.). 

 The results show con,idei-able differences : but from the accounts 

 of the experiments, Thomsen's number seems the more trust- 

 worthy. For the heat of combustion of gaseous benzene Thom- 

 sen finds the number 805,800 heat units ; Berthelot the number 

 776,000. For the heat of formation of gaseous benzene, at 

 constant volume, from amorphous carbon and hydrogen, Thom- 

 sen finds -20,120 heat units; Berthelot, on the other hand, 

 finds + 5S00. Bcnhelol does not state whether this number is 

 calculated for constant voluoie or constant pressure. Thom,en 

 makes certain theoretical deductions from the value which he 

 has found for the heat of formation of benzene, basing these on 

 his calculations for the heat of formation of "singly- and 

 doubly-linked" carbon atoms (see Natuke, vol. xxii. p. 608) : 

 lie concludes that the generally accepted hexag m formula for 



benzene is probably incorrect, and that a formula in which eacli 

 carbon atom is "singly linked " to three others is to be preferred. 



Berthelot finds the heat of formation of gaseous dipro- 

 pargyl — Cull,; — a metamer of benzene — from amorphous carbon 

 to be - 64,800 heat units. The instability and easy polymerisa- 

 tion of this body are explained by the great absorption of heat 

 which occurs in its formation. Attempts to transform dipro- 

 pargT,d into benzene were unsuccessful. Berthelot has also 

 determined the he.its of formation of various hydrocarbons, and 

 finds certain constant differences_between the successive members 

 of hom dogoas series. 



Hei;r V. Meyer describes in the Berliner Berichle a very 

 elegant modification of his method of determining vapour densi- 

 ties, whereby the specific gravities of permanent gases may be 

 rvV..dily measured at veiy high temperatures. At the highest 

 temperature of a Schliosing's furnace (about 1400") the density 

 of hydrogen vapour was normal. It has niw been shown that 

 the c'tefficients of expansion of the following gases are not 

 changed at very high temperatures : tellurium, sulphur, nitrogen, 

 oxygen, hydrogen, mercury, carbon dioxide, hydrochloric acid, 

 arsenious oxide. 



The following numbers fur the vapour densities of tellurium 

 and selenium have been recently obtained by Deville and Troost 

 (Compl. rend.) :— Selenium at 1420° = 5-68 (calcailated = 5'54), 

 tellurium at 1440° = 9'0, at 1390° = 9'o8 (calculated,j= 8'93). 



In the IVien. Acad. Beriehle Ilerr Ofler describes the results 

 of experiments which he thinks show that Guthrie's cryohydrates 

 are merely mixtures of various salts and ice : alcohol dissolves 

 the ice, leaving a ".skeleton" of undissolved salt; cold water 

 dissolves the salt, and leaves the ice with the form of the cryo- 

 hydrate. Solution of a cryohydrate is attended with the same 

 thermal change as solution of the salt and ice separately. 



The connection which exists between the opium and cinchona 

 alkaloids, and between both of these groups of compounds and 

 pyridine, has been recently made more apparent by the work of 

 Herr K. s.i^z\\i:\\^<ta (Berliner Berichte), who has shown .that 

 the so-called apophyllenic acid — obtained by oxidising the opium 

 alkaluid cotarnine — is really the acid methyl salt of pyridine dicar- 

 boxylic acid, which acid is obtained from the cinchona alkaloid 

 cinchonine, and which when heated with lime yields ]iyridine. 



When an aqueous solution of potassium, sodium, cr lithium 

 chloride, or potassium nitrate is ke])t for som; time in a vertical 

 tube, the upper part of which is maintained at a considerably 

 higher temperature than the 1 iwer part, diffusion of the salt from 

 the hotter to the colder part occurs, according to M. C. Soret 

 {Naturjorsclter). The amount of diffusion in a given time 

 depends upon the original concentration of the solution, and is 

 also connected with the molecular weight of the salt used. 



M. Dri-ET stated some little time since that the refractive 

 index of a mixture of isomorphous salts in solution is equal to 

 the mean of the indices of the components. Herr Fock (in 

 Zeitschrifi jur Crystallograp/tie) concludes, from measurements 

 of the refractive indices of solutions of thallium and | otassium 

 alums, of lead and strontium thiosulphate, and of magnesium 

 chromate and sulphate, that Dufet's statement does not hold 

 good in all cases : for the second pair of salts mentioned above 

 it is approximately correct. In Conipl. mid. Uufet gives num- 

 bers showing that his statement applies to a m.ixture of magne- 

 sium and zinc sulphates. 



In Conipl. rend. M. Demarcay describes two new compounds 

 containing sulphur, nitrogen, and chlorine, viz., SNCl and 

 (SN).|C1: the former prepared by passing chlorine into a solution 

 of nitrogen sulphide in chloroform, and the latter by adding 

 nitrogen sulphide to a solution, in chloroform, of the compound 

 SNCl. SNCl is partly decomposed by heat, in accordance with 

 the equa ion 2SNCI =N j + SjClo. 



The relation between the total energy developed in the 

 chemical reactions which occur in various kinds of galvanic 

 batteries and the energy which appears in the form of current 

 electricity, has been recently studied by Thomsen ( Wiedemann' s 

 Annalen) using a thermal method of measuring the total energy. 

 He finds that the whole of the energy developed in the chemical 

 chan/e appears as electric energy in Daniell's battery (with 

 closed circuit), and in those forms of batteries in which the 

 metallic surface of the negative electrode is not changed by the 

 electrolytic process ; when nitric acid is used as electrolyte the 

 same total conversion of one into another form of energy is 



