3. Oxyd of Zinc in the Porous Cup.-I connected four cups of Grove's battery, charged in the common method by strong nitric acid in the porous cup and sulphuric acid diluted with twelve of water, so that the zinc of the fourth cup was connected by its platinum with the acid of the first porous cup, so that there was a complete circle among the cups themselves. The action was strong and rapid; nitrous acid gas was thrown off abundantly, while no hydrogen appeared in the zinc cups. The process was suffered to go on till nearly all of both acids was consumed. After a while the porous cups began to fill with a white powder till each cup was nearly one third full. This was oxyd of zinc, and must have been derived from either sulphate or nitrate of zinc, which had been decomposed in the zinc cup or in the porous cup or both. It is more probable that the salt passed through and into the porous cup, and was there decomposed. A little nitrate of mercury was in the liquid. This appears to show the advantage of using Glauber's salt in the zinc cup in preventing the action of the nitric acid on the mercury. C. D.

Rochester, May, 1848.

4. Selenium, (Acad. Berlin, Nov., 1847.)-The specific gravity of selenium has been determined by Fr. de Schaffgotsch as follows:

For vitreous selenium,-obtained by a rapid cooling from fusion,— 4.276 to 4.286 at 20° C.; the mean is 4.282.

For fine-grained selenium,-obtained from slow cooling after heating to 250° C.,-4-796 to 4-805 at 20° C.; mean 4.801. This selenium had the aspect of hematite, and left traces on porcelain less red than the vitreous selenium.

The red selenium precipitated cold, such as is obtained by the reduction of selenic acid by sulphhydric acid, and which becomes black when moderately heated, has the specific gravity 4.259 for the red, and 4-264 for the black colored, which corresponds with that of the vitreous selenium.

5. Cause of Irised Colors on Minerals, (Soc. Sci. Göttingen; L'Institut, No. 750.)-From M. HAUSMANN's valuable memoir on this branch of optical mineralogy, we gather that the irised colors on minerals, like that on steel, is due to a thin film covering the surface; and that the colors are varied by a variation in the thickness of this film. It is of ten produced by a chemical change in the surface of the mineral, and sometimes by deposition of a foreign substance. Hydrated oxyd of iron is one of the most common of the substances that communicate irised hues. This compound results from the decomposition of pyrites, either forming first a carbonate which is common in many waters, and then by the evaporation of the water yielding the hydrate, or forming the hydrate direct. The colors on anthracite and specular iron often proceed from this source: and an exposure of the latter species to wa ters containing the carbonate, afforded Hausmann after a while, irised specimens.

Arsenic becomes irised through the action of hydrogen from the atmosphere; bismuth, by a superficial oxydation; arsenical cobalt, nickel and iron, by oxydation; galena, probably from the formation of a thin coating of sulphate of lead; magnetic iron and some ferruginous silicates, (as olivine, yenite, &c.,) from a change in the oxyd of iron to a

hydrate; pyrites, from the formation of a hydrate of iron; copper pyrites and variegated pyrites, probably from the same, the latter being very remarkable for the rapidity with which the change takes place in a moist atmosphere; antimony glance, and other antimony ores, from the formation of antimony ochre; fahlerz, and other arsenical ores, probably from the oxydation of the arsenic.

These irised colors sometimes proceed from the absorption of oxy. gen and the elimination of water, or from a disengagement of carbonic acid with a loss of water, as in spathic iron and carbonate of manganese. Irisation is often favored by heating, as in the case of steel.

6. On the Radialing Power of Substances; by A. MASSON and L. COURTÉPÉE, (Comptes Rendus, Dec. 20, 1847.)-In the experiments of Masson and Courtépée, the substances, pulverized with some water holding a little glue in solution, were applied in coats to the faces of a small cube of copper. This cube filled with boiling water was placed before a thermo-electric pile, with the radiating surfaces perpendicular to its axis. They concluded that

1. The metals have a much greater radiating power when in grains, than when melted or in mass.

2. That the radiating power of a substance depends on the cohesion of its parts, and not upon their nature.

3. That if all bodies were reduced to the same degree of chemical subdivision, they would have at 100° C., the same radiating power.

7. On Auriferous Glass; by H. ROSE, (Pogg. Annal., Ixxii, 556.)— Gold is well known to be used in making a beautiful red glass. After fusion this glass is colorless; but when heated not above a red heat, it becomes of a bright red color. Rose suggests that the gold is contained in the glass in the state of a protoxyd, which forms a colorless silicate by fusion, but sets free some portion of the protoxyd when reheated to a temperature a little below that which forms it. This protoxyd disseminated in a small quantity, in an extreme state of subdivision, is believed to give the red color. When too much heated the red changes to a brown, and Rose attributes this to the oxyd of gold becoming partly reduced and metallic gold set free. A fact, according to Rose, confirming this view, is presented by copper. For a glass containing the protoxyd of copper is colorless after fusion, a silicate being formed; but it becomes green after heating, owing to the oxyd set free. The ingredients used for the auriferous glass, are 46 pounds of quartz, 12 of borax, 12 of nitre, 1 of minium, and 1 of arsenous acid; these are moistened with a solution of 8 ducats of gold in aqua regia, and then fused.

8. Dimorphism of Zinc, (Jour. Pharm. et Chem., xiii, 18.)-Næggarath has described (Annales de Pogg., xxxix, 324) crystals of pure zinc of the form of hexagonal prisms. J. Nicklès reports that a specimen of zinc prepared by M. Favre, after Jacquelain's process, was crystallized in pentagonal dodecahedrons, like those of pyrites and gray cobalt. Zinc is therefore dimorphous. This is not the only example of dimorphism among metals. Miller has shown that tin crystallizes in square prisms (dimetric system), and Frankenheim has observed it in cubes. G. Rosè (Annales de Pogg., xlv, 319) has announced that palladium and iridium are isodimorphous, crystalling both in the rhombohedral and tesseral systems.

9. On the Estimation of Urea-Presence of Urea in the Vitreous Humor of the Eye; by M. E. MILLON, (Comptes Rendus, Jan., 1848.) -Nitrite of mercury dissolved in nitric acid gives off no nitrous vapors, but yet readily transforms urea into nitrogen and carbonic acid. The carbonic acid is collected and weighed in the usual manner in potash tubes; its weight multiplied by 1.371, gives the quantity of urea.

This method is easy of execution, consumes but little time, and is reliable to the 001 of the weight of the urine. Substances usually present in this liquid are said not to affect the accuracy of the process. M. Millon points out a curious relation between the specific gravity of urine and the quantity of urea present. The second and third figures after the decimal place in the specific gravity, very nearly represent the quantity of urea in 1000 parts of urine. This empirical law holds good only for the secretion from man in a state of health. From animals and from men laboring under various diseases no such correspondence is found.

M. Millon has also shown that the residue left on evaporating the liquid of the vitreous humor of the eye of the ox, man, or dog, contains 20 to 35 per cent. of urea-the remainder being chlorid of sodium without any albumen, as stated by Berzelius.

The aqueous humor also contains urea and chlorid of sodium.

G. C. SCHAEFfer.

10. On the Employment of Gun-cotton in Mining; by M. COMBES, (Comptes Rendus, Jan., 1848.)-It is known that this substance does not contain oxygen enough for the complete combustion of all its carbon. M. Combes proved the presence of a large quantity of carbonic oxyd, after a blast with gun-cotton, and even exploded the mixture formed with atmospheric air.

To avoid this difficulty, chlorate of potassa was added in quantity sufficient to complete the combustion-80 parts to 100 pyroxyline. The salt finely powdered was mixed with the cotton by hand. In this case the effect was excellent-no combustible vapors, no odor of any kind could be noticed; moreover, 5 parts of gun-cotton and 4 of chlorate were equal in effect to 30 parts of mining powder.

Mixtures with 80 parts nitrate potassa, or 70 nitrate of soda, were equally free from fumes and almost as powerful as that with chlorate.

In the plaster rock in which the trials were made, M. Combes asserts that these mixtures are nearly as effective as their own weight of guncotton, three times their weight of gunpowder, or four times that of blasting powder.

The volume of gas is the same with or without the mixture; the increased effect must be due to the greater heat produced by the carbonic oxyd burning to carbonic acid. G. C. S.

11. On a new Process for preparing Chloroform; by MM. HuRATET and LAROCQUE, (Comptes Rendus, Jan., 1848.)-A still with a water bath is used; into this are to be put 37 quarts of water, which are to be heated to about 100° Fahr. Then stir in 11 pounds of quick lime previously slacked, and 22 lbs. commercial chlorid of lime. Upon this pour 3 pints of alcohol of 85, and when the whole is mixed, the head is to be put on, and the water of the bath caused to boil as quickly as possible.

As soon as the heat reaches the neck of the still, the fire is to be slackened, when the distillation proceeds rapidly and continues without further beat.

The chloroform is to be separated as usual, but the liquid which floats over it is immediately employed in the following manner. Without removing any thing from the still, 10 quarts of water are to be added; when the whole has cooled to about 100° Fahr., add 6 or 8 pounds of quick lime and 22 pounds of chlorid of lime. Mix well, and pour in the liquid resulting from the preceding distillation, together with another quart of alcohol. The operation is to be conducted as before, and if the still is large enough, a third or even fourth operation may be made with advantage.

Thus, 3825 grms. alcohol gave the 1st distill'n, 550 grms. chloroform. 2d 66 640

66

The authors from an estimate conclude that this substance can be made for 14 francs the kilogramme, or $1.25 per pound. As advantages of their process, they point out the previous heating of the water, and the absence of all swelling up, owing to the use of lime and the water bath.

G. C. S.

12. On the Crystallized Hydrated Oxyd of Zinc; by M. J. NICKLES, (Ann. de Chim. et de Phys., Jan., 1848.)-The mineral known as cupriferous hydrate of zinc, contains hydrate of zinc and copper, and crystallizes in the right prismatic (trimetric) system. Anxious to ascertain whether the pure artificial hydrate of zinc belonged to the same system, it was prepared by the process of Runge. Iron and zinc are put into a vessel containing a solution of potash or ammonia; at the end of a few days the crystals are found on the sides of the vessel. These proved to belong to the same system with the mineral above named.

In the course of preparation several curious particulars were noted. The sheet zinc of commerce was readily attacked, while cast zinc refused to dissolve. The difference is attributed to the crystalline texture existing in the cast zinc, but entirely destroyed by the process of rolling the amorphous condition being always more favorable to solution than the crystalline. On the other hand, iron in the shape of turnings was found more favorable to the action than any form of wrought iron -the crystalline structure here rendering the metal more negative. In all cases the intensity of the reaction is measured by the disengagement of hydrogen. Ammonia affords the best crystals.

Lead was substituted for iron with success; also copper, when it was noticed that though there was free exposure to the air, no coloration took place, provided both metals were completely immersed. Solution of oxyd of zinc in ammonia is however decomposed by copper-the liquid becoming blue, while crystals of the hydrated oxyd are formed. The blue solution in its turn is decomposed by metallic zinc with a precipitation of copper. These reactions are cited by the author as deserving attention.

G. C. S.

13. Electro-magnetic Balance for measuring the Intensity of Currents; by M. CH. MENE, (Comptes Rendus, Jan., 1848.)-A horse-shoe of soft iron is wound a certain number of times with an insulated wire; the armature is attached to a counterbalanced scale pan. The intensity of the current is directly measured by the magnetic force developed. If the same sort of wire is used, the apparatus may be made more delicate by using a greater number of turns.

The peculiarity of this method is, that the weight supported, divided by the number of turns, represents the influence of one turn of the wi'e, that is, the intensity of the current. The recorded experiments shew a tolerable degree of accuracy in the results. G. C. S.

14. On certain properties of Iodine, Phosphorus, Nitric acid, &c.; by M. NIEPCE DE SAINT VICTOR, (Ann. de Chim. et de Phys., Jan., 1848.) The author has discovered that iodine has the property of attaching itself to the black lines of engraving, printing, writing, &c., and not at all to the white part. On this is founded a process for copying engravings, &c. The design is exposed for a few minutes to the vapor of iodine, and after moistening it in water slightly acidulated with sulphuric acid, it is applied to paper coated with starch paste, on which the copy is most accurately traced. These impressions are of course rather fugitive, and may be preserved for some time by securing them beneath a glass plate.

Several copies may be made without a second preparation of the original, and the latter proofs thus taken are the clearest.

It appears that all kinds of marks and drawing may be copied, provided gum does not enter into the writing or drawing material. For India ink and lead pencil marks, it is advised to plunge the design into a very slight solution of ammonia and then another of acid, before exposing to the vapor of iodine.

Porcelain, opal, glass, ivory, &c., when covered with starch size, gave copies of far greater beauty and permanence: they should when dry be varnished.

An iodized engraving when pressed upon a silver plate, without being moistened, leaves a very clean copy, which exposed to mercurial vapor in all respects resembles the daguerrian proofs. Copper plates require ammoniacal vapor to bring out the image, which may be cleaned by a little water and tripoli without being removed.

The black parts of a feather exposed to iodine vapor were faithfully copied while the white of the same feather was unmarked. Pieces of whitewood and ebony fastened together and the face dressed so as to be perfectly uniform, in like manner gave a copy of the black alone.

The vapor of phosphorus undergoing slow combustion, produced the same effect, the copies on metal being fixed by mercury or ammonia.

Nitric acid vapor gave renewed effects, the whites on metal being white, the blacks being represented by the pure metal surface. After using this vapor a few times the engraving will no longer give copies and must be exposed for twenty-four hours before it can again be used: with the other substances named there need be no delay.

Solutions of iodine were found to answer as well as iodine vapor. Sulphuret of arsenic (orpiment) in vapor afforded copies on metal which