Dr. Moffat had found the iodine test-paper the most sensitive, and by means of it he had often detected the gas in sick rooms and fever rooms.

On the Solvent Power of Strong and Weak Solutions of the Alkaline Carbonater on Uric Acid Calculi. By WILLIAM ROBERTS, B.A., M.D. Lond., Physician to the Manchester Royal Infirmary.

The design of the author was to show the fallacy of certain experiments that had been made on the solubility of uric acid calculi in solutions of the alkaline carbonates, and to furnish some exact data on which to estimate the rate at which it is possible to effect dissolution of these calculi by alkaline carbonates.

About twenty years ago the French Academy appointed a Commission, composed of MM. Gay-Lussac and Pelouze, to inquire and report on a number of conflicting communications that had been made to it by the advocates of solvents for urinary calculi and their opponents.

This Commission reported in 1842 to this effect:-They exposed numerous urinary calculi for a whole year to the contact of solutions of the alkaline carbonates containing from 273 to 546 grains to the pint. None of these were dissolved; and some were not diminished in bulk. Their loss of weight varied from a quarter to one-half.

In another experiment they passed 110 gallons of a solution containing a twentieth of its weight of carbonate of soda, in the course of three months, over a number of fragments placed at the bottom of a glass funnel. The bulk of most of these was not diminished, and their loss of weight varied from 10 to 60 per cent.

They then tried experiments on the living body, by passing currents of the solvent through the bladder at blood-heat by the double catheter. Here is a sample of their results. A patient who had been subjected to lithotrity, and whose stone was known to be uric acid, had at different times 55 gallons of a solution of carbonate of soda containing 132 grains to the pint, passed over a large remaining fragment which had been carefully measured. This enormous mass of liquid produced no diminution in the bulk of the fragment; its only effect was to soften the surface". The conclusions of this report were wholly adverse to the advocates of solution; and they were formally adopted by the Academy.

The experiments, however, have a defect-the solutions used were too concentrated, and this circumstance vitiates the whole inquiry. The author found that very weak solutions of the alkaline carbonates dissolved uric acid calculi with considerable rapidity, while stronger ones altogether failed. In order to decide what strength of solution had most solvent power, fragments of uric acid, weighing from 40 to 112 grains, were placed in 10-oz. phials, and solutions of carbonate of soda and potash of various strengths were passed over them at blood-heat. The expe riments were continued day and night; and the daily flow of solvent varied from six to fifteen pints.

Operating in this way, it was found that above a strength of 120 grains to the pint there was no dissolution; and even with 80 grains to the pint there was only a little; but solutions of 50 and 60 grains to the pint dissolved the fragments freely. The cause of this difference was found to lie in a coat or crust of white matter which encased the stone in the stronger solutions. At and above 120 grains to the pint, this coat was dense and tough, and could not be wholly detached from the subjacent surface. With 80 grains to the pint it was brittle, and easily detached like a layer of whitewash. With 60 grains to the pint and under, either no crust formed at all, and the stone was dissolved clean with a water-worn appearance, or it was only represented by a few loose flakes scattered here and there over the surface, and offering no impediment to dissolution. This coating or crust was found essentially to consist of biurate of potash or soda, and its formation depended on the fact that the alkaline biurates are almost insoluble in any but very weak solutions of the alkaline carbonates. In the strong solution, the biurate remains undissolved and encases the stone in an insoluble investment, while in weaker ones it is dissolved as fast as it is formed, the surface of the stone remains clean, and dissolution proceeds without impediment.

* Comptes Rendus, 1842, p. 429.

The following Tables exhibit the results of forty-eight day experiments :— TABLE I.-Uric Acid and Carbonate of Soda (Sod. Carb. Exsiccat. of the shops).

On Perchloric Acid and its Hydrates. By Professor Roscoe.

All the knowledge we possess of the quantitive relations of perchloric acid is the determination of the composition of the potassium salt, first analysed by Stadion, 1816, and afterwards by many other chemists. The perchloric anhydride has not been isolated, and no analysis of the aqueous acid has ever been made. We can only account for the neglect with which chemists have treated the highest and yet the most stable of the oxides of chlorine by the fact that the preparation of the acid in larger quantities has been attended with great difficulties. The best method for preparing aqueous perchloric acid is to decompose chlorate of potassium with hydroffuosilicic acid, and to boil down the chloric acid thus obtained; this splits up into lower oxides of chlorine, which escape in the gaseous state, impure perchloric

8

acid being left behind, which is purified by distillation. The acid thus obtained is in appearance not to be distinguished from oil of vitriol, being a colourless, heavy, thick, oily, corrosive liquid, giving off on heating dense white fumes. By hearing the aqueous perchloric acid with four times its volume of concentrated sulphurie acid, the latter takes water from the first, dense white fumes are evolved, a yellow mobile liquid distils over, and afterwards thick oily drops appear, which, when coming in contact with the yellow liquid, form the white crystals, previously obtained by Serullas, but in such small quantities that he was unable to analyse the substance, which prepared in this way always contains sulphuric acid, and is therefore not fit for analysis and requires redistillation. Heated, however, to 110° C., the crystals decompose and split up again into the yellow liquid, which distils over at a low temperature, and the thick oily liquid, which remains in the retort. The yellow liquid thus obtained is pure perchloric acid, CI O, H, a body not known before, which can be obtained also by distilling one atom of perchlorate of potassium with four atoms of sulphuric acid. In the pure state it is perfectly colourless, but as commonly prepared it is slightly yellow, owing to the presence of lower oxides of chlorine. Perchloric acid is one of the most powerful oxidizing agents known: a single drop brought into contact with charcoal, paper, wood, alcohol, &c., immediately causes explosive combustion, in violence not falling short of the decomposition of chloride of nitrogen; and brought on the skin wounds are produced, which do not heal for weeks. Like nitric acid it cannot be distilled without decomposition, but it darkens, and ultimately decomposes with explosion. It cannot be kept for any length of time; for even when sealed up in glass bulbs which are placed at the ordinary temperature in the dark, it decomposes suddenly after some time, breaking the vessel containing it. It mixes with water with a hissing noise and evolution of heat, forming the same crystals which were mentioned before, and were used for preparing the pure acid. These crystals are the monohydrated perchloric acid, C1 OH+H2O. They melt at 50° C., and heated to 110° C. split up in pure perchloric acid, which distils over, and an oily liquid boiling at 200°, which is also obtained by boiling aqueous perchloric acid till dense white fumes are given off. This oily acid has a constant composition, containing 72.3 per cent. of pure perchloric acid and 27.7 per cent. of water. This per-centage corresponds, however, to no definite hydrate of simple atomic composition; and therefore this acid follows the same general relations respecting composition and boiling-point which, as I have shown previously, hold good for so many other aqueous acids, namely, that the phenomenon of constant boiling-point and constant composition depends chiefly upon physical and not upon chemical attractions.

On Vesicular Structure in Copper. By Drs. RUSSELL and MATTHIESSEN. The authors proved by numerous experiments that the vesicular structure is caused by the action of carbon or sulphur on the suboxide dissolved in melted copper.

On certain Difficulties in the way of separating Gold from Quartz.

By Dr. SMITH of Sydney.

In Australia the usual plan is to reduce the quartz to powder by Cornish stampers, a stream of water being allowed to flow through the stamp box during the operation. The pounded quartz is carried by the stream through fine gratings, and then along an inclined plane supplied with various contrivances, such as blanket stuff and plates of copper rubbed over with mercury, for detaining the gold. The stream is next conducted into the basin of a Chilian mill, where the "pulp" is ground up with mercury. These operations are for the most part so successful as to leave not more than half an ounce of gold in a ton of “tailings." But this successful result is only attained when the quartz is free from pyrites. When pyrites is present, particularly a black amorphous variety (found by Dr. Leibius to contain disulphide of copper and sesquisulphide of iron), there is a notable loss both of gold and mercury in the process of amalgamation. In the basin of the Chilian mill a greyishblack scum might then be seen, which contains mercury and gold in fine division, together with various components of the pyritous quartz, buoyed up by the entanglement of air. The action upon the mercury appeared to be chiefly mechanical,

but also in some degree chemical, a small portion of sulphide of mercury being found in the scum, while the gold extracted contained a much larger proportion of copper than is usual with Australian gold. The Australian miners appeared to have hit on no economical mode of separating the gold from pyritous quartz, so as to avoid this loss.

On a Specimen of Meteoric Iron from Mexico. By Professor TENNANT.

On the Cohesion-Figures of Liquids. By CHARLES TOMLINSON. Regarding solution as a case of adhesion, the author showed that when a drop of an independent liquid (i. e. not a solution) is placed on the surface of another independent liquid, such as water, a struggle takes place between them. The particles of the drop endeavour to maintain their cohesion, the adhesion of the surface tends to overcome it; hence a well-defined figure, named by the author a cohesionfigure, and regarded as the resultant of the cohesion of the liquid, its density, and the adhesion of the surface. For example, if a drop of oil of lavender be gently delivered to the surface of water in a chemically clean glass, about 3 inches in diameter, it is spread out by the adhesion of the surface into a well-defined film; cohesion then endeavours to reassert itself, and a struggle takes place between the two forces, the result being a beautiful complicated pattern resembling Carrigeen moss. The cohesion-figures of other oils, fixed and volatile, of creosote, ether, alcohol, naphtha, &c. were shown experimentally, or in the form of large diagrams. In order to produce these figures, the glass vessels and the water must be chemically clean. The figures present a variety of novel and beautiful effects, both as to form and colour, and are likely to prove highly suggestive to the pattern-designer. Moreover, the forms being typical of the substances, a ready means is thus afforded of detecting adulteration.

On the Composition of Crystallized Moroxite, from Jumillo, near Alicante. By Dr. VOELCKER, F.C.S.

Beautifully crystallized moroxite occurs in large quantities at Jumillo in Spain. Selected crystals of this mineral, analysed by the author, give the following results:

The oxide of cerium is not present in the form of Kryptolite, since the analysis was made with perfectly transparent light-green-coloured crystals.

The matrix in which the moroxite crystals are imbedded consists almost entirely of calc-spar.

On the Composition and Properties of the Water of Loch Katrine, as supplial in Glasgow. By Dr. WALLACE, F.O.S.

The water of Loch Katrine is well known to be remarkably pure, and to have the property of acting upon lead more extensively than any other natural water known, if we except rain-water. This latter circumstance induced several of our most eminent chemists to express the opinion that danger to the health of the people of Glasgow might arise from the introduction of the water.

The distance of the lake from the city is about 35 miles, and the author shows that the water becomes altered very considerably in composition during its transit. A minute and careful analysis of the water was made in February last; and for comparison an analysis of the true Loch Katrine water, made in the spring of 1854, is also given, the numbers representing grains per gallon.

In the Loch Katrine water no carbonate of lime was found, while a direct determination of this compound in the Glasgow water gave 68 grain per gallon. This carbonate of lime is supposed to be derived from sandstone and other rocks through which the water flows.

Loch Katrine water gave 7.5, and Glasgow water 8-5 cubic inches of gas per gallon, which contained in 100 parts—

The difference in the total quantity of gases may be owing to variation of temperature. The increase in the carbonic acid, accompanied by a corresponding decrease in the oxygen, appears to be owing to the oxidation of organic matter, a similar change occurring when the Loch Katrine water is kept in a closed vessel for a week or two.

Experiments on the action of the Glasgow water on lead show it to be much less active in this respect than the original water of Loch Katrine, the quantity dissolved during the first twenty-four hours being about one-third, and the ultimate result after several weeks, the water being renewed every twenty-four hours, rather more than half of the quantity dissolved by the original water under similar circumstances. At the end of a month the proportion of lead dissolved by the Glasgow water appears to remain steady at th of a grain of lead per gallon, a quantity that is just upon the verge of danger.

On the large scale, with pipes and cisterns in actual use, the proportions of lead dissolved were smaller. Three sets of experiments were made; with an old -inch pipe previously employed for two years for the conveyauce of Clyde water, a new 1-inch pipe, and a new cistern exposing 24 square feet of surface to each cubic foot