METALLURGY. (ALUMINUM.) 



355 



tained in specially designed vats, heated by waste 

 steam, and kept in a state of agitation for from 

 one to three hours. By this means the extraction 

 of the total gold contents from refractory ore was 

 greatly facilitated. Ores, slimes, etc., after being 

 subjected to the action of the chemicals, are ready 

 for treatment by amalgamation. 



It has been observed by W. Witter that at a 

 gold mill in the province of Smfiland, Sweden, 

 where the water used in the stamp mill is taken 

 from a river running from peat moors, while the 

 amalgamation of the ores takes place without dif- 

 ficulty in seasons of full water, at periods of low 

 water and when the weather is dry the copper 

 plates are covered with a green slime, which al- 

 most prevents the mercury from taking up any 

 gold. This effect of the water remained, notwith- 

 standing all methods employed to counteract it. 

 As soon as the green slime was rubbed off the 

 plates it formed again rapidly, and it finally 

 became necessary to stop amalgamation during 

 the dry season. Yet experiments made in the 

 laboratory at Hamburg with exposure of bright 

 copper plates to the water led to no result. 



In a course of Cantor lectures before the British 

 Society of Arts on the nature and yield of metal- 

 liferous deposits, Mr. Brewster H. Brough said of 

 gold, that in 1898, of a total product of 57,- 

 500,000, the Transvaal produced 27.6 per cent., 

 Australasia 22.5 per cent., the United States 22.1 

 per cent., Russia 8.8 per cent., Canada 4.8 per 

 cent., Mexico 3 per cent., India 2.7 per cent., and 

 China 2.1 per cent. Thus the Transvaal, Austra- 

 lasia, and the United States together produced 72 

 per cent, of the whole. In view of the present 

 conditions and prospects, the lecturer concluded 

 that there were no signs of failure in the world's 

 gold production. 



For the treatment of gold and silver containing 

 considerable quantities of zinc, for which ordinary 

 retorts are not suitable, B. Sadler has patented 

 a peculiarly constructed retort. It has a body 

 of fire clay or equivalent material with its inner 

 surface coated with a sintering substance adapted 

 to combine chemically under suitable firing with 

 the fire clay and also with the basic material. 

 This sintering substance may also be applied to the 

 more exposed parts of the outer surface of the 

 fire clay. A further lining or coating of basic 

 matter is then applied to the fire clay. The en- 

 tire body is subjected immediately before using 

 to firing at a temperature ranging about 1,500 

 F. for two or three days. With a retort of this 

 nature the ore after roasting can be satisfactorily 

 freed from zinc by distillation, while the gold, 

 silver, copper, iron, and about 60 per cent, of the 

 lead are left in the residue, which, being oxidized 

 and containing some carbon, is suitable for treat- 

 ment in a smelting furnace. The patentee defines 

 as the essential feature of his process the conduct- 

 ing of the distillation under such conditions as 

 will exclude the corrosive action and mischievous 

 chemical combinations which would result if the 

 oxides or corrosive agents had access to the fire 

 clay or other ingredients of the retort for which 

 they have chemical affinity, and in combination 

 with which their action would be destructive. 



The German official tests for silver-plated goods 

 are chromate and sulphide reagents. The chro- 

 mate reagent is a mixture of equal weights of 

 potassium bichromate and nitric acid. A drop 

 of this liquid on the plated surface leaves a brown 

 <>r red stain on the silver. This reagent, even in 

 a dilute form, is not available when the coating 

 of silver is very thin. The sulphide reagent is 

 a 1 .5-per-cent. solution of sodium disulphide. A 

 drop of this should leave a gray stain, but the 



results are often very doubtful. A. Munkert pro- 

 poses dissolving the layer of silver from the goods 

 and testing the solution. The best solvent is a 

 mixture of 10 cubic centimetres of concentrated 

 sulphuric acid with 5 drops of pure nitric acid, 

 both acids being free from chlorine. The metal 

 to be tested is cleaned with alcohol and ether 

 or chloroform, and is then placed in a dry test 

 tube and covered with the acid mixture. The 

 silver coating dissolves readily in the cold, and 

 when the color of the underlying metal is clearly 

 visible the acid is poured off, diluted with twice 

 its volume of water, and one or two drops of dilute 

 hydrochloric acid 1:10 are added. The extent of 

 the turbidity viewed against black paper is to 

 some extent an indication of the quantity of sil- 

 ver, but in the case of large articles the silver 

 may be estimated quantitatively. 



Of 165,000,000 ounces of silver extracted in 1898, 

 Mexico produced 34.4 per cent., the United States 

 33 per cent., and Australasia 7.3 per cent. Less 

 than half the world's supply was obtained from 

 silver ores. The remainder was procured from the 

 metallurgical treatment of other ores in which 

 silver was an accessory constituent. Since these 

 ores would continue to be mined for the other 

 metals they contained a steady supply of silver 

 was assured, while a slight rise in the price of 

 silver would enable many deposits of true silver 

 ores now untouched to be worked. 



The only places where platinum is known to 

 occur in North America otherwise than as a min- 

 eral curiosity are in California, Oregon, and Brit- 

 ish Columbia. Many reports of its occurrence were 

 not substantiated when Mr. D. T. Day made his 

 investigation of the subject. Although a number 

 of deposits are known on the Pacific coast, the 

 platinum in them is very fine and difficult to 

 save. Most of the platinum product has come 

 from inland diggings, where the grains are closer, 

 particularly from the placers of the American 

 river and those in Plumas, Shasta, Trinity, and Sis- 

 kiyou Counties, California. These occurrences con- 

 firm the idea that the platinum originates in the 

 serpentine rock in which the region abounds, for 

 the platinum-bearing gravels are sure to be asso- 

 ciated with some prominent serpentine ridge. 

 The value of platinum metals in a large num- 

 ber of the platinum-bearing gold sands of Cali- 

 fornia and Oregon ranges from nil to $1,934 

 per ton. They contain generally less platinum 

 than gold, but occasionally more, even up to three 

 times the quantity, platinum being generally less 

 than the other platinum metals, in proportions 

 ranging from one sixth to one half. 



Aluminum. Speaking in the Franklin Insti- 

 tute of recent advances in the aluminum industry. 

 Prof. Joseph W. Richards said that in the line of 

 pure metallurgy, or reduction and refining, there 

 was little to chronicle. The process of reduction 

 had certainly been somewhat improved in details, 

 but in principle it was the same as the Hall pro- 

 cess of ten years ago. The operators of the process 

 were naturally averse to publishing the details of 

 their method, but it might be said that all 

 the items of expense had been gradually notched 

 down, so that the cost price of the metal had 

 been reduced to about 20 cents a pound, while 

 its selling price was a little more than 30 cents 

 in the United States and 25 cents abroad. As was 

 proved by certain instances adduced by the author, 

 aluminum has become cheaper for almost every 

 practical purpose for which it can be used than 

 all the common metals excepting zinc, lead, and 

 iron. In verifying this statement it should be 

 borne in mind that aluminum is only about one 

 third the weight of these other metals, and that 



