on diluting with cold water, the whole of the copper is precipitated as a white powder; the clear solution, if the process is completed, will contain no copper, when there will be two equivalents of copper dissolved from the metal for every equivalent of peroxide of iron formerly in the solution. It occasionally happens, however, when neutral salts of iron are used, that the copper becomes encrusted with a white deposit, upon which crystals of the subchloride of copper collect, and thus protect it from further action; this is prevented by boiling, or taking out the copper, removing the crust, washing it, and putting it into the solution again, when the action goes on as before. When the persulphate of iron is used for this purpose instead of perchloride, no subsalt is formed, and the result is uniform, one equivalent of copper being dissolved for every equivalent of peroxide of iron present in the solution.

I may mention one especial application of the solubility of copper in perchloride of iron, namely, the dissolving copper from the surface of silver, such as copper that has been used as a mould in which silver has been deposited; when this solution becomes saturated with copper, a little ammonia added precipitates the iron as a peroxide, and combines with the copper, forming a soluble double chloride, which may be immediately separated by filtration and the precipitate washed, the peroxide of iron again dissolved in hydrochloric acid is fitted for a renewal of the same operation. I may here mention, that if, previous to adding the ammonia, there be a little perchloride of iron put into the mixture of subchloride of copper and protochloride of iron, an immediate change is effected, the colour of the solution becomes green, and on adding ammonia to this, both copper and iron are precipitated.

Persulphate of iron cannot be used for the purpose of dissolving copper from silver, both from the easy solubility of silver in solutions of this salt, and also from a peculiar destructive action which it has upon alloyed silver. Standard silver is completely destroyed. I have used thin sheets, weighing from 60 to 70 grains, and when only 4 grains were apparently dissolved, the remainder had been so much affected that it crumbled between the fingers like a dried leaf.

When silver is put into a solution of persulphate of iron an immediate action takes place, a yellowish cloud begins

to form in the solution; if heated the action is much more rapid, a yellow oxide of iron forming upon the sides of the vessel, and there is also a brown precipitate deposited; the iron in the solution is converted into the proto state, shining particles of metallic silver float through the solution, and sulphate of silver crystallizes on the vessel, but in no case did I find an equivalent of silver for the equivalent of peroxide of iron; by slow evaporation the solution yielded crystals of protosulphate of iron and sulphate of silver.

Tin is very easily dissolved in both the persulphate and perchloride of iron, completely reducing them to the proto state. When the solution is cold this is effected in about an hour; when hot, in a few minutes; the iron is reduced to the proto state when only half an equivalent of tin is dissolved for every equivalent of peroxide; my first impression was, that the first atoms of protosalt of tin formed reduced a corresponding atom of peroxide of iron, and was converted into a persalt; but saturating with ammonia, and adding it in great excess, the precipitated oxide of tin was not redissolved, and had every other character of a protosalt. Whether this was owing to the formation of a bisulphate or bichloride of tin, I did not ascertain; but by boiling or long standing there is an equivalent of tin dissolved for every atom of perchloride of iron, but I did not obtain the same result in the persulphate.

Cadmium is very soluble in persalts of iron; in the persulphate an equivalent of cadmium is dissolved for the equivalent of persulphate of iron; but in perchloride of iron two equivalents of cadmium are dissolved for every equivalent of perchloride of iron, forming, as in the case of copper, a subchloride, which was not precipitated by the addition of water.

Lead is also dissolved in persalts of iron, reducing a portion of the iron to the state of a proto salt; the lead becomes covered with a thin crust of sulphate or chloride, which seems to protect it from further action; when the iron solution is boiled with the lead much more is dissolved, and a precipitate of peroxide of iron collects at the bottom. This action of iron on lead may account for the rapid destruction of leaden tanks, noticed by Mr. West at the last Meeting of the British Association, that when

spring water, which had been running into a lead tank for many years without the slightest action upon the lead, was conveyed through iron pipes to the tanks, the tanks were destroyed in six years.

Antimony is not very soluble in persulphate of iron even when heated, but it is very soluble in perchloride of iron when hot, reducing the iron to a protochloride in a short time, the solution becoming of a light brownish colour. I found that if kept boiling slowly for a long time the antimony loses an equivalent of metal for every equivalent of peroxide of iron, giving us the idea of the existence of a compound of antimony with chlorine of one to one. This solution was not examined further than by dilution with water, which precipitated almost all the antimony as a white powder, undergoing the usual changes of common chloride, except when the dried precipitate was boiled in nitric acid, in which it dissolved with the evolution of nitrous gas.

Arsenic is very soluble in perchloride of iron, reducing the iron to the state of protochloride, losing also with long boiling an equivalent of metal for every equivalent of peroxide of iron in the solution; but this result is not obtained without long boiling.

Bismuth is very soluble in perchloride of iron, slightly in persulphate; the perchloride is completely reduced to the state of protochloride, a full equivalent of metal being dissolved for the peroxide of iron present; this is wholly precipitated by dilution.

Cobalt is very soluble in perchloride of iron, reducing it completely, changing the solution to a pink colour; the cobalt salt formed crystallizes from this solution very easily.

Nickel is also soluble in perchloride of iron, giving a precipitate of brown oxide of iron; the solution becomes green, containing protochloride of iron and nickel; a portion of the nickel is precipitated as a fine white powder by dilution.

Platinum in persulphate and perchloride of iron produced no change, neither lost anything in weight.

Gold boiled for a long time in perchloride of iron in two experiments lost 0.2 and 0.3 of a grain. In both these instances beautiful crimson-red crystals, in perfect octahedrons, were obtained, adhering to the metal and also to

the containing vessel. I did try whether they contained any gold. These results were only obtained twice in six different trials; they were procured with iron prepared at different times. Platinum was always tried at the same time with the gold, and when there was no gold dissolved I never obtained any crystals.

I need hardly mention that both zinc and iron, when put into the persalts of iron, first reduce the persalt to the protosalt, which fully accounts for the great consumption of iron for the small quantity of copper obtained in these waste waters of mines, and not, as was generally supposed, from the existence of free acid; the copper is never all precipitated from the water so long as persalts of iron exist in the solution. The presence of persalts of iron also prevents the deposition of the copper by a galvanic current; the proportionate quantity of persalts of iron necessary to resist completely the deposition of copper was not ascertained.

In no one case did I find any double salt formed between the iron and metal dissolved in it, but when the solution containing them was evaporated, the salts of the two metals crystallized separately.

In all cases where the process is conducted cold, the solution of the metal takes place at the bottom of the vessel and progresses upwards; this is beautifully exhibited when a tall glass is used with a solution of perchloride of iron, and a slip of copper reaching to the bottom; the solution first becomes green at the lower part, and this advances slowly upwards till it reaches the top, but before the change of colour reaches the top, the bottom has become colourless from the formation of subchloride.

I may observe that the whole of these remarks are only the prominent features noted down as they occurred, without any idea of bringing them before the Society in this unfinished state; but having no hope of obtaining leisure for making further investigations, I have given them as they are, thinking that perhaps some one, having more time and ability, would repeat the experiments and produce something more definite.

LAW REPORTS OF PATENT CASES.

Vice-Chancellors' Courts, Wednesday, July 24.
(Before Sir L. SHADWELL.)

BUNNETT AND CORPE v. SMITH.

THIS was a motion on behalf of Messrs. Bunnett and Corpe, the patentees of "certain improvements in the construction of safety metal window shutters," for a special injunction to restrain the defendant, Andrew Smith, from manufacturing or selling a shutter of a similar construction, which was alleged to be an infringement of the patent. The plaintiff, Bunnett, claimed to be the author of the invention, for which a patent was granted to him in 1836, and was represented chiefly to consist in a series of strips, or plates of metal connected together by hinges, that the plates partially overlapped each other, and entirely concealed the hinges, no portion of the plates being cut away at the edges at those places where the knuckle of the hinges came as in similar metal shutters before constructed, and the plates so connected were wound up by means of an endless screw and a toothed wheel. The shutters which the defendant had recently put up at the banking-house of Messrs. Smith, Payne, and Smith, in Mansion-house-place, which was alleged to be an invasion of the patent with a mere colourable variation, appeared to differ only in the mode in which the process of winding up was effected, which on the one side was contended to be so essentially different as not to come within the principle of the specification, and on the other to be merely the use of a chain instead of a succession of hinges, which was practically as well as in principle the same. plaintiff's patent was also attacked on the ground of want of novelty, and the imperfect language of the specification in the description of what it was the plaintiff claimed as his invention.

The

Mr. Bethell, with Mr. Bacon, moved for the injunction; and Mr. Stuart and Mr. Turner were counsel for the defendants.

The Vice-Chancellor said, that where a patent was found to have existed for a period of eight years without