484 



MAUCH, KARL. 



A dinner in the Harvard Memorial Hall in the 

 afternoon, and a promenade concert on the 

 common in the evening, concluded the pro- 

 ceedings. Among the minor celebrations of 

 the year was one at Gloucester on the 9th of 

 August, in memory of an encounter between 

 the citizens of that place and the British sloop- 

 of-war Falcon. 



MAUCH, KAEL, a German explorer, born at 

 Ludwigsburg in 1837 ; died April 5, 1875. He 

 studied in London, traveled in 1860-'66 

 through the Transvaal Republic, crossed the 

 water-shed of the Zambesi and Limpopo, and 

 penetrated almost as far as the neighborhood 

 of Tete on the Zambesi. In 1867 he journeyed 

 in a more northwesterly direction, discovered 

 two paying gold-fields, explored in 1868-'69 

 Maselikatse from Limpopo to Inyati, and in 

 1870 undertook a journey to the Delagoa 

 Bay. In 1871 he found, in latitude 20 14' 

 south, and longitude 31 48' east of Green- 

 wich, 41 miles from the port of Sofala, the 

 ruins of Zimbabye, whose extreme antiquity 

 is proved by the fact that the walls are made 

 of hewn granite, without mortar. An account 

 of these ruins, and the gold and diamond fields 

 found in the neighborhood, caused Mauch and 

 Petermann to believe that these plains were 

 the land of Ophir spoken of in the Bible, where 

 the Phoenicians obtained their gold, ivory, and 

 precious stones. After returning to Germany, 

 he engaged in commercial pursuits. His death 

 was caused by a fall from the third story of 

 his house to the pavement below. 



METALS. Gallium. This is the name given 

 to a new metal discovered by M. Lecoq de 

 Boisbaudran, of France. The discovery was 

 first publicly announced in a note from M. 

 Lecoq de Boisbaudran, presented by M. "Wurtz 

 to the Academie des Sciences at its meeting of 

 September 20, 1875. Particulars were com- 

 municated under seal on the 27th of the pre- 

 vious August. This new element was first 

 found in the chemical examination of a blende 

 from the mine of Pierrefitte, in the Pyrenees. 

 It has not yet been obtained by itself, traces 

 of zinc and cadmium being constantly asso- 

 ciated with it. From a study of the chloride 

 and sulphate of gallium, salts that have been 

 produced in a nearly pure state, the follow- 

 ing properties, as detailed in Nature, have been 

 made out : 



1. Its spectrum consists of two lines, one much 

 brighter than the other, both situated in the violet, 

 the regions occupied by the brightest lines of the 

 zinc, the place of the former line being at the 417th 

 degree of the scale, and the other at the 404th. The 

 electric spectrum of the chloride is very brilliant ; 

 the color of the spark is a beautiful clear violet. 



2. In the gas-flame only the line Ga a 417, very 

 faint, and fugitive even with a salt which gave a 

 brilliant electric spectrum, was obtained. 



3. The chloride and the sulphate of Ga are pre- 

 cipitated by NH 3 , but the precipitate is redissolved, 

 m great part, in an excess of NH 3 . Taking up with' 

 HC1 the portion not dissolved by NH 3 , and recom- 

 mencing the operation, all the Ga is promptly ob- 

 tained in ammoniacal solution. 



METALS. 



4. An ammoniacal solution of sulphate of chloride 

 of Ga is precipitated in the cold or hot state by an 

 excess of acetic acid. The liquor must be extremely 

 diluted. 



5. The chloride and the sulphate of Ga are not 

 precipitated in the cold state by the acid acetate of 

 ammonia, but the reaction takes place on heating. 



6. The sulphate of Ga is soluble in a 60 per cent, 

 alcohol solution. 



7. A salt was obtained which the author believes 

 to be ammoniaco-gallic alum ; though, in default of 

 sufficient quantity, he was unable to analyze it or 

 measure the angles. 



8. The alum of Ga is soluble in cold water, but, on 

 heating, the Rait is decomposed, and the liquor be- 

 comes greatly troubled. 



9. This alum is not decomposed in the hot state 

 by water with addition of acetic acid. 



10. It crystallizes very easily in cubes and octahe- 

 dra, presenting exactly the aspect of ordinary alum ; 

 its solution, evaporated under the microscope, also 

 presents the characteristic changes of known alums. 



11. The crystals do not act on polarized light (be- 

 tween two Nicols giving extinction). 



12. A small crystal was kept some time under a 

 laye* of water, then transferred to a slightly super- 

 saturated solution of alumino-ammoniacal alum ; it 

 immediately increased in it, and caused the crystal- 

 lization of the liquor. 



13. With ammonia in excess, the alum of Ga be- 

 haves like the other salts of this metal ; a portion 

 of the oxide is precipitated, the other portion re- 

 mains in solution. 



14. The very acid solution of Ga 2 Cl a is precipitated 

 by the yellow prussiate. 



15. The ammoniacal solution of sulphate of Ga is 

 decomposed by the voltaic current. Metallic gallium 

 is deposited on the platinum plate serving as nega- 

 tive electrode. The positive electrode is covered, 

 at the same time, with a whitish pellicle, which is 

 easily detached from the platinum, and is insoluble 

 in a large excess of NH 3 . In a first operation 1.6 

 mgr. of Ga were deposited in 4 h - 30 m - on a platinum 

 plate of about 185 square millimetres surface. The 

 surface of the positive electrode was about 877 sq. 

 mm. The battery consisted of five bichromate cou- 

 ples (zincs: 17 cm. x 10cm.) coupled in tension. 

 The author presented to the Academy a specimen 

 weighing 3.4 mgr. ; it was deposited in 5 h - 40 m - on a 

 surface of about 123 to 124 sq. mm. The positive 

 electrode 877 sq. mm. ; the current furnished by ten 

 bichromate elements (as above) coupled in tension. 



16. Electrolytic gallium forms a very adherent 

 layer; it is hard; 'it is polished with difficulty by 

 friction with an agate burnisher. A better polish 

 is obtained by strong compression under the bur- 

 nisher ; the metal thus acquires great brightness, and 

 appears whiter than platinum. When the electric 

 current and the relative dimensions of the electrodes 

 are properly regulated, the gallium presents a beau- 

 tiful dull surface of silvery white, finely granulated, 

 and interspersed with small brilliant points, which 

 the microscope shows to be crystals. 



17. Gallium deposited on a platinum plate is not 

 much oxidized during washing in cold or boiling 

 water, nor on being dried in free air raised to about 

 200. It decomposes water acidulated with HC1 in 

 the cold state, and more rapidly in the hot state, 

 with a brisk liberation of hydrogen. 



The salts of Ga which M. Lecoq de Boisbaudran 

 has used in his researches have been from the blende 

 of Pierrefitte ; he has, however, found the new metal 

 in other ores of zinc, and notably in a transparent 

 blende from Santander. He believes Ga will be met 

 with in all blendes. The Ga he extracted from the 

 blendes comes really from these minerals, and not 

 from metallic zinc. 



The author's last researches have confirm e^ the 

 rarity of gallium in blende. The extreme sensibility 

 of the spectral reaction led him even to over-estimate 



