524 



METALS. 



in the weight to be carried. If trie bronze plate 

 were two-thirds the thickness of the iron plate, the 

 cost would be equivalent, while the resisting power 

 would be greatly in favor of the bronze. If we chose 

 to carry the same weight of bronze that is now sus- 

 tained in the shape of iron, we should in accordance 

 with the present hypothesis double the resisting 

 power of the armor. The great dynamic force of the 

 projectile may interfere with the accuracy of our de- 

 ductions, although this would seem to be met by the 

 quality of toughness to which we have referred, and 

 the perfect homogeneity of the metal, as illustrated 

 by its symmetrical contraction in diameter when 

 elongated under the breaking-strain. 



Assaying Chrome-Iron Ore. Prof. W. Ditt- 

 mar's new method of assaying chrome-iron ore 

 differs from other methods chiefly in the mode 

 of disintegration, which in his process is found- 

 ed upon two facts hitherto unnoticed, viz. : 1. 

 The fact that powdered chrome-ore is easily 

 dissolved, not only, as is known, by fused 

 borax, but also by a ready-made flux obtained 

 by fusing together borax with an excess of 

 alkaline carbonate ; and that 2. The mixture 

 thus formed, when kept in a state of fusion in 

 contact with air, readily absorbs oxygen, with 

 conversion of the whole of the chromium into 

 alkaline chromate. The process is as follows : 



Two parts of borax-glass are fused together with 

 three parks of the mixture NaKC0 3 in a platinum 

 crucible, until the eliminated carbonic acid is com- 

 pletely expelled, the mass poured into a large plati- 

 num basin, allowed to cool, and bottled up for use. To 

 disintegrate an ore, fuse one-half gramme of it with 

 five to six grammes of the flux in a covered crucible 

 over a Bunsen's lamp, and maintain a dull-red heat 

 for about five minutes. Now open the crucible, lay 

 it slantingly on the triangle, and, while maintaining 

 the highest temperature attainable with a Bunsen's 

 lamp, stir up the mixture with a platinum wire until 

 the ore is completely dissolved. This being accom- 

 plished, continue heating the fused mass in presence 

 of air for about half to three-quarters of an hour. 

 Then allow to cool, digest the tused mass in water 

 until it is completely disintegrated, heat on a water- 

 bath with addition of a few drops of alcohol (to re- 

 duce any manganate that may be present), and, after 

 having evaporated away the alcohol, filter and wash 

 the residue with hot water. The filtrate contains 

 the whole of the chromium as chromate, which is 

 most conveniently determined by an inversion of 

 the well-known process of Penny for the determina- 

 tion of feiTosum. The form in which the author 

 prefers to execute this titration is to dissolve aknown 

 weight of metallic iron in hot dilute sulphuric acid, 

 to cool down the solution as rapidly as possible, to 

 add the previously acidified chromate, and then to 

 titrate back with a standard solution of bichromate 

 of potash. 



Prof. Dittmar has applied this process a good 

 many times, and always found it to disintegrate the 

 ore completely in one opsration ; and when applied 

 repeatedly to identical samples, he found it to give 

 perfectly constant results. Be never saw two anal- 

 yses of the same ore to differ from each other, by 

 more than 0.3 in the percentage of oxide of chro- 

 mium. He has satisfied himself by special experi- 

 ments that none of the chromium, which is once 

 dissolved, rem dns unoxidized (i. e., is obtained as 

 chromite instead of chromate), and that the insolu- 

 ble basic borates obtained in treating the fused mass 

 with water, when dissolved in dilute sulphuric acid, 

 yield a solution which is free from chromium. But 

 this solution invariably contains something else, 

 which, as Prof. Dittmar never saw his crucibles visi- 

 bly attacked through the fusion-process, he did not 



expect to find, namely, a very appreciable quantity 

 of platinic salt. It is on account of this constituent 

 that it is not admissible to simplify the process by 

 dissolving the whole of the fluid mass, en bloc, in 

 dilute acia, and applying the titration-process to this 

 solution. 



Gallium. The new metal gallium, discov- 

 ered by Lecoq de Boisbaudran in a blende from 

 Pierrefitte, was first isolated during the past 

 year by its discoverer, and its physical prop- 

 erties determined. Having obtained about 

 ten centigrammes of gallium in the metal- 

 lic state, M. de Boisbaudran found that the 

 pure metal melts at about the temperature of 

 29.5 C. ; hence it is liquefied when held in the 

 fingers. When once solidified it is hard and 

 resistant, even at temperatures only a little be- 

 low its melting-point. Melted gallium adheres 

 readily to gla^s, forming a fine mirror, whiter 

 than that produced by mercury. When heated 

 to bright redness in presence of air, gdlium is 

 only oxidized very superficially, and is not 

 volatilized. In the cold it is not sensibly at- 

 tacked by nitric acid, but with the aid of heat 

 it dissolves, emitting red fumes. The specific 

 gravity of gallium is 4.7 at the temperature of 

 15 C., water at the same temperature being 

 1. A communication from M. de Boisbaudrau 

 to the Paris Academy of Sciences contains the 

 following record of observations on liquid gal- 

 lium : 



1. A very small globule, exposed to the open air 

 for more than three weeks, lost neither its liquidity 

 nor its metallic lustre. 



2. The metal is deposited upon a negative elec- 

 trode of platinum as a dead, whitish-gray coating 

 formed ot numerous minute globules. It dissolves 

 in the cold in dilute hydrochloric acid with brisk 

 disengagement of hydrogen. 



3. The hydrochloric solution of the metal yields a 

 fine spectrum of gallium ; along with the zinc-rays 

 more feebly. The latter are less marked than with 

 the solid gallium from the ammomacal solution. 



4. The residue from the limited evaporation of the 

 hydrochloric solution of the liquid metal is neither 

 colored by iodide of potassium, nor by ammonia, 

 nor by hydrosulphate of ammonia. The drv residue 

 from the evaporation was nevertheless sufficient to 

 be distinctly visible. Mercury, therefore, is not pres- 

 ent. 



5. Liquid gallium, deposited by electrolysis upon 

 a small piece of platinum, was heated to redness, or 

 almost to redness. It adhered and doubtless became 

 alloyed with the platinum ; and resisted the action 

 of hydrochloric acid, but it was attacked, by weak 

 aqua regia along with a little of the platinum ; the 

 solution showed the rays of gallium. A slight whit- 

 ish pellicle, insoluble in aqua regia, was detached 

 from the platinum; this was, perhaps, oxide of gal- 

 lium rendered insoluble by ignition. 



It is the author's opinion that pure gallium 

 is liquid, and that its solidity is caused by the 

 presence of relatively inconsiderable quantities 

 of foreign metals. 



The spark-spectrum of gallium gives the two 

 bright lines of wave-length 417 and 403.1 ; its 

 flame- spectrum only the 417 line, and that 

 faintly. 



In a later communication to the same Acad- 

 emy, M. de Boisbaudran thus describes his pro- 

 cess of extracting gallium : 



