614 



NATURE 



{Oct. 19, 1882 



during the summer of 1881, has returned to Chicago, and has 

 recommenced his valuable measures of double stars with the 

 large refractor. The present report has an engraving of this 

 instrument, and of the tower of the Dearborn Ob;ervatory, in 

 which it is mounted. 



Comet 18S2 b (Finlay, September S). — The following 

 positions of this comet are deduced from the elements published 

 in Nature last week : — 



At l8h. Greenwich M.T. 



CHEMICAL NOTES 



MM. Hautefeuille and Chafpuis have obtained what 

 appears to be pure liquid ozone, by compressing a mixture of 

 oxygen and ozone at 125 atmospheres, and cooling the end of the 

 capillary tube by a jet of liquid ethylene : on suddenly releasing 

 the pressure, a drop of a very deep indigo-blue liquid remained 

 in the end of the tube. The gas above this liquid was colourless, 

 but as the last traces of liquid evaporated, the gas was seen to 

 have a blue colour (Compt. rend. xciv. 1249). 



It is well known that sulphuretted hydrogen produces little or 

 no precipitate in an aqueous solution of arsenious oxide : accord- 

 ing to the experiments of Messrs. H. Schulze (Journal fur 

 pract. Chemie, 2, xxv. 431), such a liquid contains a colloidal 

 form of arsenious sulphide. This colloid may be completely 

 separated from dissolved arsenious oxide by prolonged dialysis ; 

 the solution, if dilute, is scarcely changed by long-continued 

 boiling ; the presence of free acids or of such soluble salts as 

 chloride of potassium, iron, or chromium induces a change of 

 the colloidal into an insoluble form of arsenious sulphide. 



By strongly compressing phosphoretted hydrogen in presence 

 of water, and then suddenly decreasing the pressure, M. Cailletet 

 has obtained a crystalline hydrate of this compound, the exist- 

 ence of which is conditioned by the temperature and pressure ; 

 the critical point, i.e. the temperature above which the substance 

 cannot exist, whatever be the pressure, is 28°. Hydrates of 

 sulphuretted hydrogen and of ammonia have also been obtained 

 by this method (Compt. rend., xcv. 58). 



By a somewhat similar process, M. Wroblewski has obtained 

 a solid crystalline hydrate of carbon dioxide,C0 2 . 8H a O : the 

 experimental results of this author seem to show that at the 

 pressure required to cause the absorption of carbon dioxide by 

 water in the proportion indicated by the formula C0 2 . H„0, 

 the water would be entirely frozen, and therefore that this 

 hydrate cannot be obtained by this method (Compt rend., xciv, 

 1355)- 



"When solution of two salts, capable of mutual action, are 

 mixed, the solution contains four salts": it has hitherto been 

 difficult to give a direct experimental proof of this generalisation 

 made half a century ago by Berthelot. In the last number of 

 the Berichte of the German Chemical Society (15, 1840) Herr 

 Briigelmann describes the following experiments designed to 

 prove the justness of Berthelot's statement: — Equal volumes of 

 cold saturated solutions of cobalt chloride and nickel sulphate 

 are mixed and allowed to deposit crystals by evaporation at ordi- 

 nary temperatures ; the crystals contain cobalt and nickel, but 

 combined with sulphuric acid only. A mixture of solution of 

 cobalt chloride and copper sulphate, prepared similarly to the 

 preceding, deposits sulphate of the two metals almost free from 

 chlorides. Copper sulphate and potassium dichromate solutions 

 when mixed deposit crystals consisting almost entirely of sul- 

 phates of copper and potassium, the second crop of crystals con- 

 tain a little chromate of the two metals, and the final crop is 

 nearly free from sulphates. 



The "Compagnie Generale des Cyanures et Produits Chi- 

 miques"of Paris have issued a small pamphlet explanatory of 

 the various technical applications of the salts known as sulpho- 

 cyanates, which can be now readily manufactured in a state of 

 purity. Sulphocyanate of aluminium is used as a mordant in 



alizarine dyeing ; silpbocyanate of copper in the preparation 01 

 aniline black, and also, along with potassium chlorate and anti- 

 mony sulphide, in the preparation of matches ; sulphocyanate of 

 potassium may be employed as a refrigerating material, as during 

 the solution of 130 parts of this salt in 100 parts of water, tem- 

 perature is lowered through 34 ; sulpho-cyanate of ammonium is 

 more effectual, weight for weight, as an antichlor, than hypo- 

 sulphite of soda. 



Investigations conducted at the Baden Aniline and Soda 

 Works show that the change of orthonitro phenyl propiolic acid 

 into indigo, which (as already explained in this journal) has 

 been for the most part effected by grapes or with sugar, can 

 also be produced by the agency of sulphides, sulphydrates, poly- 

 sulphides, thiocarbonates, and especially the alkaline xanthates 

 (Chemisches Centralblatt, 1S82, 366). 



GEOGRAPHICAL NOTES 

 News has been received from the expedition of Dr. Emil 

 Riebeck, dated July 7 last. It will be remembered that Dr. 

 Riebeck, together with Dr. Schweinfurth made a thorough in- 

 vestigation of the island of Socotra, which was of high scientific 

 importance. After this task was accomplished, the travellers 

 separated, and Dr. Riebeck crossed to Bombay, travelled 

 through large tracts of the Himalaya Mountains, remained for 

 some time in Cashmere, then passed through the Ganges land, 

 investigated Ceylon, and eventually undertook a special and 

 detailed examination of the coast district of Aracan. He 

 ascended the Karnasuli River from Tschittagong as far as the 

 Hill tribes, to which Prof. Bastian has drawn special attention. 

 He made many measurements, took numerous photographs and 

 plaster casts of this highly interesting tribe, which is still living 

 in a most primitive natural state. The climate, however, and 

 particularly the frequent fording of rivers, soon told upon Dr. 

 Kiebeck's health. He contracted a fever, and had to be taken 

 to Singapore. His valuable collections of zoological, anthropo- 

 logical, and ethnological specimens duly attracted the attention 

 of geographers, and were frequently referred to at the recent 

 " Geographentag." Since then Dr. Riebeck has continued his 

 journey. Starting from Singapore, he is to follow the eastern 

 coast of the Asiatic continent, then to cross over to Australia 

 and New Zealand, and finally to return to Europe next summer 

 by way of San Francisco and Panama. 



To the Berlin Geographical Society the other evening, Major 

 von Mechow gave tome account of his explorations during the 

 last year or two in the region of the Coango. Leaving Berlin in 

 September, 1878, accompanied by a ship's carpenter and a 

 gardener, Major von Mechow arrived at Dundo on the Coanza 

 in the following January ; but, owing to various difficulties, it 

 was the beginning of 1880 before he could start northwards into 

 the interior at the head of 115 native carriers. Crossing and 

 re-crossing the Cambo, and passing through various powerful 

 and hospitable tribes, the German traveller, after a thirty-seven 

 days' march, at last reached the Coango on July 19, 1S80, and, 

 under the guidance of the great chief Tembo Aluma, visited the 

 magnificent Succambondu waterfall, which he named after the 

 Emperor William. After canoeing it on the Coango for twenty- 

 five days, Major von Mechow made a detour to pay his respects 

 to the great Muene Putu Kassongo, by whom he was received 

 in great state, and returning on September 19 to the river, he 

 followed it to longitude 5 deg. 5 min., from which point the fear 

 of his followers of the neighbouring cannibals compelled him to 

 return. In forty-five days he again reached the abode of 

 Kassongo, where he stayed some time, and at last arrived on 

 February 20, 1SS1, at Malange, where he met his returning 

 countryman, Dr. Buchner, as well as Herr Pogge and Lieut. 

 Wissmann, who were both starting on a similar tour of explo- 

 ration. 



A German edition of Amici's "Morocco " has been published 

 by Ilartleben of Vienni. Herr von Schweiger-Lerchenfeld is 

 the editor, and has to a considerable extent remodelled the 

 work, adding interesting ethnographical and historical notes, 

 and omitting passages and references which in the original work 

 can only interest Italian readers, on account of their purely 

 private and local character. Its scientific value is also consider- 

 ably increased. Two new chapters have been added, one on 

 Southern Morocco, the other on the war between Spain and 

 Morocco in 1S60, and these are not the least attractive ones in 

 the book, quite apart from the geological interest attaching to 



