METALLURGY. 



527 



The special feature of Mr. J. Holme Pollok's 

 process for the extraction of gold is the man- 

 ner of chlorinating under hydraulic pressure, 

 which, it is represented, enables the chlorine 

 to extract the gold more completely, in a 

 shorter time, and at less expense than by any 

 other mode of treatment. In trials with re- 

 fractory ores and tailings which, when treated 

 by the ordinary processes, have yielded only a 

 small proportion of their gold, almost the 

 whole of the gold is said to have been extract- 

 ed in nearly every case. The earliest attempt 

 to use chlorine in gold extraction, about 1864, 

 was found to be so expensive that the process 

 never came into use. An improvement on this 

 was made by Mr. Means, of America, who 

 pumped chlorine gas into the cylinder. A 

 later invention is that of Messrs. Newbery and 

 Vautin. 



Gold is described by Mr. R. W. Maclvor as 

 occurring in quantities in a matrix of serpen- 

 tine at Gunidagai, in Xew South "VTales, where 

 it exists as tine flakes distributed irregularly 

 through the rock. The appearance is as if the 

 metal had been painted on the rock-surfaces 

 by the hand. The yield of gold ranges from a 

 few pennyweights to several ounces per ton. 



Ores of auriferous tellurium are analyzed by 

 F. M. Horn by gently heating them, finely 

 powdered, in a current of dry chlorine. The 

 author succeeded equally well by treating the 

 mineral with hydrochloric acid, witli the addi- 

 tion of a little nitric acid. Besides silver, gold, 

 arsenic, antimony, tellurium, copper, and lead, 

 there are generally quantities of iron, zinc, lime, 

 magnesia, sulphur, and sulphuric acid, which 

 are determined by the usual methods. 



Silver. In a paper at the Australasian Asso- 

 ciation on silver-smelting, rich silver mattes 

 and their treatment, and on "kernel roast- 

 ing," Mr. Edgar Hall showed that the main 

 object of the smelter was to get clean slags. 

 He did not consider that the dissemination of 

 matte globules satisfactorily explained the losses 

 of silver ; for he had detached perfectly pure 

 crystals from the very heart of the pot from 

 slags of every kind, which yet often contained 

 more silver than the main body of the slags. 

 He thought that "high" silver slags might be 

 due to the property possessed by silver of pass- 

 ing from already solidified portions of a body 

 in which it is present into any portions which 

 still remain liquid. 



Silver has been detected by J. "W. Mallet in 

 the ash of the volcano of Cotopaxi, in the pro- 

 portion of one part in 83,600 of the ash, or 

 about two fifths of a troy ounce per ton of 

 2.240 pounds. This seems a small proportion, 

 but it mast represent a very large quantity of 

 silver ejected during the eruption (July 22, 

 1885), when ash fell at Bahia de Caraguez to 

 the depth of several inches. 



Mr. Gowland, of the Japanese mint, has 

 found that when small quantities of bismuth 

 are present in silver, as is often the case when 

 silver is obtained from copper containing bis- 



muth, the metal is brittle and lacks uniformity, 

 the parts which solidify last being richer in 

 silver. The coinage bars prepared from this 

 silver can not be rolled without special treat- 

 ment, and even then are hard and unsuitable 

 for mintage. 



Alloys. The following results were reached 

 in Prof. E. J. Houston's experiments on the 

 magnetic relations of palladium alloys in watch- 

 es: A watch whose balance-wheel, hair-spring, 

 and escapement are made of the Paillard pal- 

 ladium alloys can not have its weight sen.-il>ly 

 affected by the influence of any magnetic field 

 into which it is possible to bring it while on 

 the person of its wearer. Experiments showed 

 that the palladium alloys are destitute of para- 

 magnetic properties. As far as the amount of 

 the alloys at the author's disposal permitted, 

 experiments failed to show that they possessed 

 any diamagnetic properties. In four of the 

 alloys described by Mr. Paillard the complete 

 masking of the paramagnetic properties of 

 some of the ingredients would seem to indicate 

 a true chemical union of their constituents. 

 The most interesting results of these experi- 

 ments, however, were those in which it was 

 established that no matter of what materials 

 the balance-wheel or hair-spring may be made, 

 provided they are conductors of electricity, 

 their movements through a magnetic field, 

 when the moving masses properly cut the lines 

 of force, must result in a change in the rate of 

 their movement, and consequently in a change 

 in the rate of the watch ; or, briefly, it was estab- 

 lished that a watch placed in a magnetic field 

 acts like a dynamo-electric machine. The fact 

 that the watch subjected to this experiment, 

 after its removal from this powerful field, did 

 not manifest any sensible change in its rate, 

 shows the extent of the protection the palla- 

 dium alloys give it against the effects of exter- 

 nal magnetism. 



The experiments of T. H. Norton ard E. H. 

 Twitchell with alloys of calcium and zinc had 

 in view a clear examination of the alloys and 

 an inquiry into their availability for the pro- 

 duction of metallic calcium. Some of them were 

 made with the proportions indicated by Caron, 

 who claims to have made alloys containing 

 from 10 to 15 per cent, of calcium ; and in 

 others the amount of zinc was reduced by one 

 half. An alloy containing 2'28 per cent, of 

 calcium was very hard to distinguish from pure 

 zinc. Two alloys formed from preparations 

 containing half of Caron's proportions of zinc, 

 contained respectively 5 - 44 and 6 - 06 per cent, 

 of calcium. In the two succeeding experi- 

 ments, Caron's proportions were restored, and 

 the resulting alloys contained 4'97 and 6'36 per 

 cent, of calcium. In all efforts to obtain al- 

 loys richer in calcium, although zinc was driven 

 off in notable amounts, there was still a pro- 

 portionate loss of calcium. The residual alloy 

 rich in calcium was left in so spongy a con- 

 dition that it oxidized immediately in contact 

 with the air, and the crucibles showed traces 



