510 



METALS. 



He was also the author of "The Protector; 

 or, the English Republic in the days of Crom- 

 well ; " " Three Centuries of Scottish Struggle ; 

 or, Two Kingdoms and Two Kings;" "The 

 Character of the Reformer and the Reforma- 

 tion of Geneva." He published also, in 1848, 

 an interesting account of his personal travels 

 under the title of "Germany, Scotland, and 

 England ; or, the Recollections of a Swiss Min- 

 ister," together with a number of sermons, 

 addresses, and special papers, the latter having 

 been principally contributed to the periodical 

 known as the Arc/lives du Christianisme. His 

 personal influence at Geneva was very great, 

 as it was wherever his name and his writings 

 were known. 



METALS. Gold in Sea- Water. Mr. E. Son- 

 stadt recounts in the London Chemical News his 

 long- con tinned endeavors to detect the presence 

 of gold in sea-water, and separate it. All his 

 methods were applied directly to the sea- 

 water, and not to the residue left on evapora- 

 tion. The water tested by him was obtained 

 at different times from different parts of Ram- 

 sey Bay, Isle of Man, and the results in all the 

 cases were in entire accordance. The propor- 

 tion of gold in sea- water (containing less than 

 a grain in a ton) is 7nuch too small to admit 

 of separation or even detection by the ordinary 

 means; and there is another difficulty men- 

 tioned by Mr. Sonstadt, namely, the continu- 

 ous resolution of the gold after it has been sep- 

 arated in the metallic state. The first method 

 he describes is on some accounts the best, as it 

 can be practised on so small a quantity of 

 water as 150 or 200 c. c. 



Two or three decigrammes of pure ferrous sul- 

 phate are dissolved in the water, which is acidulated 

 by two or three drops of hydrochloric acid. The 

 solution is heated in a chemically clean and well- 

 glazed porcelain dish, over a small flame, so man- 

 aged that the flame may touch the under part of the 

 dish without causing ebullition. Under these cir- 

 cumstances, a lustrous film of ferric oxide forms in 

 the dish, commencing from the portion directly 

 heated by the flame. The heat is continued, without 

 boiling, until the sea-water is evaporated to about 

 half, or so long as the film increases in extent and in 

 lustre. The liquid is then poured oft', the strongly- 

 adherent film is rinsed with a little water, and then 

 about 50 c. c. of strong chlorine-water is allowed to 

 stand in the dish for an hour or two, after which it 

 is slowly evaporated down (over the film) to a few 

 drops, a drop of dilute hydrochloric acid being added 

 toward the end of the evaporation. The liquid, 

 which should be nearly colorless, is then poured in- 

 to a test-glass, containing a few drops of solution of 

 stannous chloride, when, after a few minutes, the 

 liquid takes a bluish or purplish tint, which may be 

 exactly matched by a drop or two of a suitably dilut- 

 ed solution of gold added to a corresponding portion 

 of tin-salt in another glass. The reaction may, of 

 course, be made more striking by taking for th'e ex- 

 periment a larger quantity of sea-water, although the 

 reaction obtainable from the quantity indicated is 

 quite definite. I have repeated this experiment 

 many times, upon different specimens of sea-water, 

 and always with the same result when "A film was ob- 

 tained on evaporation. But the formation of this 

 film depends upon the iron being in a particular de- 

 gree of oxidation, and I have sometimes failed to 

 obtain it. The best way is, after adding the ferrous 



sulphate and hydrochloric acid to the sea-water, to 

 leave it exposed to the air for a few hours, or over- 

 night, before heating the liquid to obtain the film. 

 Corresponding experiments were made, in the same 

 vessels and with the same reagents, upon simplo 

 water, and upon water containing chloride of sodium 

 and alkali sulphates in solution, but the films ob- 

 tained, when treated as described, never gave the 

 slightest coloration with solution of stannous chlo- 

 ride. The chlorine solution off the sea-water films 

 may be dried up in a porcelain crucible with precipi- 

 tated lead, and gold beads obtained by cupellation, 

 after fusing the lead into a button with borax ; but, 

 for this experiment, at least half a litre of sea-water 

 should be taken, and even then the bead obtained is 

 not ponderable. 



Assay of Pyrites for Gold. Mr. J. M. Mer- 

 rick describes in the American Chemist his 

 method of assaying pyrites for gold. H< 

 takes 1 Ib. or even 18 oz. of fine, smooth dm 

 and mixes it with 8 oz. of finely-pulverized am 

 sifted pyrites ; the whole is then resitted, 

 put into a Hessian crucible, which should be 

 about one-third filled with the mixture. The 

 crucible is then exposed to a common fire of 

 hard coal, and, during the first half-hour, the 

 contents are stirred once or twice ; and, as the 

 fire grows brighter and carbonic-acid gas is 

 evolved, the mixture should be stirred evei 

 five or ten minutes. The author continues : 



On stirring during this time, the iron rod seems 

 meet with but little resistance from the light mass 

 but, at the end of about one and a half hour, the 

 evolution of gas suddenly ceases, the red-hot mass 

 becomes heavy, sinks, and requires considerable 

 force to keep it stirred. It must be stirred well and 

 vigorously, however, for about half an hour, not 

 leaving it unstirred for more than a minute, other- 

 wise the mass will fuse or cake, and the assay will 

 be almost inevitably ruined. 



When a sample taken out in an iron spoon gives 

 off no smell of sulphur, the entire contents ot the 

 crucible must be turned into a stoneware pot or a 

 wooden bucket half filled with water, and well 

 stirred. When the powder which should be uni- 

 form and free from lumps or fused pieces has set- 

 tled, the water must be poured off, the wet mass al- 

 lowed to drain, and then transferred to a large earth- 

 en bowl or porcelain mortar. Here it is to be amal- 

 gamated with about 2 oz. of mercury, to which a lit- 

 tle bit of sodium amalgam has been added. The 

 amalgamation, as well as the stirring in the fire, is a 

 tedious process, and one which I prefer to do by 

 proxy. It does not consist in merely grinding with 

 a pestle the mercury in among the particles of the 

 roasted ore, but this ore itself must be ground in 

 contact with the mercury, until the particles are so 

 fine that they will float suspended in water for sev- 

 eral seconds. At the end of, say, ten minutes' 

 thorough grinding, the contents of the bowl are to 

 be brought into one mass in the bottom of the ves- 

 sel, the bowl then sunk in a tub of water, and the 

 contents " washed down" nn operation not easily 

 described, but familiar enough to every old Califor- 

 nian. It consists essentially in shaking the bowl half 

 full of ore and water in such a way that the mercury, 

 gold particles, and unground ore, sink to the bot- 

 tom, while the light arid finely-ground ore is floated 

 off into the tub. The ore remaining is reground 

 and rewashed, and these processes are repeated till 

 nothing but the mercury remains in the bottom of 

 the bowl or mortar. This mercury is then dried 

 with filter-paper, and heated in a porcelain capsule, 

 over a Bunsen flame, very gently, until it is sub- 

 limed, and the gold remains behind. The film of 

 gold may then be scraped up and melted, with a lit- 



