Edward Sonstadt

Popular Science Monthly, Volume 2, pp255, 1872

posted Jun 16, 2017, 2:03 AM by John Doe

Gold In Sea-Water.—In a series of researches on the composition of sea-water, a chemist named Sonstadt has been able to make out the presence of gold as one of its constituents. It appears to be completely dissolved, and is held in solution by the action of iodate of calcium, which, as shown by the same chemist, sea-water also contains. He demonstrates the presence of gold by three separate and entirely different methods, and estimates the proportion to be less than one grain per ton of water.

Ueber die Gegenwart des Goldes im Meerwasser

posted Jun 16, 2017, 1:41 AM by John Doe   [ updated Jun 16, 2017, 1:49 AM ]

von E. Sonstadt.

Aus Chemical News durch den American Chemist, December 1872, S. 206.

Zur Entdeckung des Goldes im Meerwasser habe ich mich drei ganz verschiedener Methoden bedient; sie wurden aber sämmtlich auf das Wasser selbst, nicht auf seinen Verdampfungsrückstand angewandt. Die Wasserproben schöpfte ich zu verschiedenen Zeiten an mehreren Stellen der Bucht von Ramsey auf der Insel Man, und die Resultate von allen diesen Proben stimmten völlig untereinander überein. Der Gehalt des Meerwassers an Gold (sicherlich weniger als 1 Gran engl. per Tonne = 20 Centner) ist zu gering, um eine Trennung oder selbst Entdeckung mit den gewöhnlich angewandten Mitteln zu ermöglichen. Außer dieser Schwierigkeit stellt sich noch eine andere von größerem Gewichte in den Weg, welche auf der beständigen Wiederauflösung des Goldes, nach seiner Abscheidung im metallischen Zustande, beruht. Diese Wiederauflösung rührt her von dem Freiwerden des Jods unter dem Einflusse reducirender Agentien auf den jodsauren Kalk, welcher, wie ich schon früher nachgewiesen habe, im Meerwasser vorkommt. Selbst wenn das reducirende Agens in sehr großem Ueberschusse zugesetzt worden ist, nimmt unter der fortwährenden wieder bildenden Kraft des Kalkjodats die Oxydation so rasch zu, daß früher oder später, je nach dem Ueberschusse des gegebenen Reagens, der Zeitpunkt eintritt, wo Jod frei und das suspendirte Gold wieder aufgelöst wird. 

I. The first method for the discovery of gold in seawater to be described here can be carried out successfully with 150 to 200 cubic centimeters of water. In the water, acidified with two or three drops of hydrochloric acid, two or three decigrams of pure sulfuric acid are dissolved, and the solution is heated in a porcelain dish so moderately that no boiling occurs. In this case, a shining cuticle  of iron oxide is formed in the shell  , which emanates from the position first determined by the flame. The heating is continued until about half the water has  evaporated, or as long as the pellicle of expansion and luster still increases. Then the liquid is poured off, the cuticle hanging on the shell is rubbed with a little water, sets 50 cubic meters. Cent. Add one drop of hydrochloric acid towards the end, and pour this almost colorless liquid into a test tube, which already contains a little tin chloride solution. Within a few minutes, a bluish or purple color will appear.

The result always occurs safely, when, on the first evaporation, the mentioned cuticle has been produced; But the formation of the latter is due to the fact that the iron is, to a certain extent, partly due to higher oxidation. In order to achieve this purpose, I have found it best to leave the seawater, after being mixed with the iron vitriol and the hydrochloric acid, for some hours or overnight, before the warming and evaporation are carried out.

The chlorination of the skins can also be allowed to dry in a porcelain crucible containing precipitated lead, and by means of cupelation, gold spheres are obtained after the lead has been melted with borax into a bead; But at least 1/2 liter of seawater is required, and even then you can not get any weighable globules.

II. The second method requires 1/2 to 1 liter of seawater. It is treated with so much solution of pure chloride of barium that the precipitate thus formed is about 1 gram. 1 to 3 days are required for complete discontinuation. The precipitate is collected, dried, mixed with borax and lead, melted before the blowpipe on charcoal to a bead, and subjected to the cupelation. The bead thus obtained has a yellowish-white color similar to that of an alloy of 60 parts of gold, and 40 parts of silver. In order to confirm the presence of the gold, the bead is dissolved in a few drops of royal water in a tube, evaporated almost to dryness, a few drops of hydrochloric acid are added, and evaporated to expel the rest of the nitric acid.

This experiment is delicat and requires much circumspection. 39)

III. The third method is the one by which I have first convinced myself of the presence of gold in seawater; But it has the disadvantage of greater difficulty than the two preceding ones. At least one liter of seawater, which is placed in a stopper bottle, is placed a few grams of iron vitriol, two or three days later a solution of chloride of chloride of chloride, and the solution of mercuric chloride, but no excess of the latter, but only so much that a new additive still contains an excretion of mercury Cause. Neither the precipitate produced by the iron sulphate, nor the precipitate produced by the stannous chloride, tear down the gold, but only when the mercuric chloride is added, does the mercury separated by the reaction of the stannous chloride draw upon the gold and silver present, And thus falls out as an amalgam. The iron vitriol can also be omitted, but more tin chloride is required, and this oxidises itself in the sea water so rapidly that it is feared that the precipitated gold will be dissolved again by the iodine (which was already mentioned above). If only solution of tin and mercury has been employed, the precipitate may be calcined, tested in the usual manner, and the obtained beads treated as described under II. The experiment, however, is annoying because of the many tin oxide underneath. If, however, the precipitate contains ferric oxide, the ordinary test method fails because the ferric oxide is reduced to metal during the melting process, even in low reddish-brown, and the spongy iron closes the gold and silver before the lead is admitted. It is therefore necessary, in the examination of substances containing a considerable amount of ferric oxide, to avoid the reduction as much as possible by applying only borax as a flux, in such a ratio that the iron oxide remains completely dissolved. That not the reducirende but only the oxidising blowpipe must gain ground, goes without saying. 40)

The reagents used in all these experiments had previously been carefully examined for a possible content of noble metals, and with each series of experiments I made comparative samples with rainwater, always with negative results. I have thought of the dissolving effect of very dilute solutions of iodine on gold. The following experiment confirms this effect. A precipitate of pre-precipitated gold was added to concentrated hydriodic acid, which was weakly colored by free iodine, but was quite pure in the rest. The acid soon became turbid. 1 to 2 drops of this solution were added to a concentrated solution of stannous chloride, and immediately gave the gold-purple reaction; The liquid which appeared was colorless, and remained so after the addition of stannous chloride. After a few days the liquid smelled of iodine, And the addition of stannous chloride again gave rise to gold purple, a proof that iodine was liberated, and had dissolved again from the precipitated gold. After a further one or two days, however, gold was dissolved, and tin chloride was thrown down again. This experiment could be repeated several times with success.

Since gold is easily reduced in very dilute solution by organic matter, and by sunlight, it was important to ascertain how far the sea-water differs from the ordinary water in relation to the behavior to gold, or, better, Gold in the presence of organic matter. This force, as the following experiment shows, is the iodic acid contained in the sea water. 41)  One drop of gold solution was  added to 400 cubic centimeters. Cent. Rainwater, divided this mixture into two equal parts, and added to the same 1/10 volume of a solution of lime iodate containing 1/1000 of the salt. Further, a drop of the same gold solution was added to 400 KC sea water, and another drop was added to a corresponding quantity of lime iodate solution. The cups, in which these four liquids were located, were placed uncovered in the sun. All four, with the exception of the sea-water, took a distinct color within a few hours, and on the following day looked distinctly red. After the course of one or two days, however, they all appeared almost colorless, with the exception of the pure gold solution, which remained permanently colored. The disappearance of the color can only be explained by the redelution of the precipitated gold, while the precipitation itself is out of the question. So dilute red liquids lose their color, without even a few months being perceived. I have done several similar experiments under different circumstances, and all showed that the iodic lime does not act on the gold, Nor to prevent its reduction from its solution. But as soon as the iodate itself undergoes a partial decomposition under the influence of rotten matter, iodine is dissolved and the gold present dissolved.

Polytechnic Journal, 1873, Vol. 207, No. LXIII. (P. 211-215)

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