that the whole had the effect of a bronze, while at the beginning of the experiment before the eye had become fatigued, it was easy to distinguish between the violet of the chlorophyl and the livid green of the flesh color.

Employment of the Sodium flame by artists.-We have previously shown that the different colors of the spectrum may be reduced to white or black, unless they contain blue which is the only color unaffected by the soda flame.

In observing such a spectral image it will be noticed, that if all the colors are reduced to either white or black, the borders are more or less darkened or dulled as in a photograph of the spectrum. Looking at a painting, especially a pastel containing very little if any blue, under these conditions, one is struck with the fact, that although the colors vanish, the grayish tone which represents them gives the appearance of a pencil drawing. The model or plan exists by reason of the half tints so that by the monochromatic light, one is sometimes able to go back to the design without touching the picture and can thus give in some sort the autopsis of a work of art.

The flame of sodium may yet aid the painter in comparing shades, in grouping colors and weighing their tones.

In the same manner, two colors, for example two greens which appear identical upon the palette, in the daytime, may be different when seen by common evening light, and are more likely to differ when viewed by the sodium flame, one being decolorized and the other transformed into black. In the same manner, of two reds seen under the same conditions, one may appear white, while the other containing blue, will assume a violet-tint complementary to the yellow of the monochromatic flame.

Common salt ignited on a platinum wire in the flame of a Bunsen burner, strikingly exhibits the chemical differences which sometimes exist between two similar shades of color. This means may be useful in distinguishing original pictures from copies, for it is not likely that Raphael or Van Dyck, for instance, exployed exactly the same pigments as their copyists have used.

If one desire to render the flame of a gas burner or of an oil lamp monochromatic, it cannot be done with NaCl, for the flame is not hot enough to volatilize that compound. Metallic sodium should be used for this purpose, which may be introduced into the gas burner or held in the flame upon platinum wire.

Perchlorid of Lead, PlC.-In connection with what we said last year (this Journal, [2], xli, 107 and 55) upon the halogen compounds corresponding to the peroxyds, we have since obtained the compound PbCl corresponding to the peroxyd of lead PbO. Unstable in a free state, it may be preserved for a long time in presence of a solution of chlorid of calcium.

It is prepared by passing a current of chlorine into chlorid of

lead held in suspension in a solution of CaCl of 40° Beaumé. The liquid becomes yellow and acquires very curious properties. Thrown into a small quantity of water, it gives a precipitate of PbCl with excess of water a brown precipitate is formed of PbO2. PbCl3+2HO+Aq=PbO2 +2C1H+Aq.

In this case the hydrochloric acid does not react, because of the excess of water present, if there were less the result would PbO2+2CIH=2HO+PbCl+Cl.

be

The perchlorid of lead does not act upon the nitrate of bismuth, behaving in this respect differently from TIC13 (this Journal, [2], xli, 107). When heated it blackens cane sugar but not glucose, and hence may serve to distinguish between these two kinds of

sugar.

Treated with anhydrous ether and syrupy phosphoric acid, the solution of perchlorid of lead thickens, and yellow oily drops appear, which are perchloro-plumbic ether. This ether readily dissolves gold, and as the metal is taken up chlorid of lead separates assuming the form of the gold employed. The perchloroplombic ether readily decomposes; the products are protochlorid of lead and chlorinated ethers. The ease with which chlorine separates from it, is the cause of its solvent power on gold, in which respect it is like the bodies presently to be noticed.

New solvents for Gold.-The perchlorids dissolve gold readily when that metal is in the form of leaf, on account of the facility of their decomposition with liberation of chlorine. If ethereal solution of perchlorid of manganese be employed, the green color of the manganese compound grows lighter in proportion as the gold dissolves, for MnCl2 is reduced to MnCl, and the reaction is complete, when the liquid has exchanged its green color for the yellow of the solution of gold, (it is the same with MnBr3 and MnI2).* On evaporating the liquid, a film of gold adheres to the vessel. The same solution added to FeO SO3 yields the precipitate of gold so characteristic for its dichroism.

The sesquichlorids, and the sesquibromids which are easily reduced-for example, the compounds corresponding to Mn2O3, Ni203, Co203; also Fe2 Br3 even in presence of a certain proportion of FeBr-dissolve gold; Fe I3 is also a good solvent for gold especially in presence of ether. It is only necessary to add a small quantity of Fe2O3 to the ethereal solution of iodhydric acid, in order to dissolve the metal. This proves that iodine in the nascent state acts upon gold. For this reason gold is acted upon even by iodhydric acid in presence of ether. No action takes place when only water is present. It can no longer be said with truth, that free iodine does not act upon gold. I have found that gold may be dissolved by it in presence of water,

*This Journal, [2], xli, 107.

when put into a close vessel and raised to a temperature of 50°. The action is more slow if ether is used in place of water. Exposure to strong sunlight will hasten the solution.

Some new facts concerning amalgamation.-In vol. xli, p. 225 of this Journal, Prof. Silliman has described some properties of the magnetic amalgam, composed of mercury and sodium. The following experiment readily shows the great difference between the action of mercury and that of sodium amalgam.

Take a square of glass, to which apply side by side two. leaves of beaten gold. If a drop of ordinary mercury be placed on one of these leaves, it adheres without sensibly increasing in area. On the contrary a small drop of the amalgam spreads out with great rapidity, so that in a few seconds the mercury has covered a space many hundred times larger than that which the original drop occupied.

I showed in 1853 (in this Journal)* that the metals moistened by mercury are permeable to it; that proposition has been verified upon the metals since discovered or prepared, viz., thallium, aluminium and magnesium. Thallium is easily amalgamated, and becomes brittle by the penetration of mercury; on the contrary, magnesium and aluminium resist its action or are not wetted by it until recourse is had to electric action, such as is realized by the intervention of sodium or zinc.

It would be interesting to observe the deportment of indium toward mercury. If it were capable of being moistened it would form with it a brittle amalgam; on the other hand, if it were not moistened it would retain all its elasticity. I leave the question to those who are fortunate enough to possess this metal so rare, and so difficult to obtain in a metallic mass.t

Chemical synthesis.-M. Berthelot continues his beautiful researches in synthesis, and is at present occupied with the generation of hydrocarbons. Our readers know that he formerly obtained acetylene, CH3, by the direct union of hydrogen and carbon (this Journal, 1862). Berthelot has lately shown that a whole series of hydrocarbons, polymeric with CHI3, may be derived from it as follows:

This table is the result of actual experiment and not of theoret

ical speculation.

* J. Nicklès, On the Permeability of Metals to Mercury, [2], xv, 107.

A sheet of platinum that has been for four months in contact with amalgam

of sodium still preserves all its elasticity.

Berthelot has observed still another series of hydrocarbons, between styrolene and retene, the boiling point of which is between 250° and 340°, and which possess to a great extent the characteristic fluorescence of pyrogenic oils of resin. Berthelot regards these hydrocarbons as C'H' six, seven, and eight times. condensed. Between 210° and 250° there passes over a liquid which, when placed in a freezing mixture, yields crystals of naphthaline. The origin of this interesting hydrocarbon is easily explained, naphthaline being in fact only pentacetylene less H2.

Naphthaline is produced equally well when acetylene is passed into a tube heated to redness. There is, however, in this case but a small quantity formed, for the acetylene is chiefly decomposed into carbon and hydrogen.

Acclimation of the Camel in Australia.-The introduction of the camel into Australia has been previously announced, and it was effected by the "Société d'Acclimatation." We now learn that these animals have adapted themselves to that country, as has been shown by a recent expedition consisting of seventy horses, fourteen camels, and fifteen men. The springs of living water upon which they depended having been dried up, sickness broke out in the camp. The men fell back upon their stores of spirituous liquors, the horses took to flight, while the camels alone remained at their post. It is owing to this circumstance solely that the expedition was reorganized. At last accounts the caravan had arrived at Thompson river.

Acclimation of the Salmon.-The eggs of the salmon which have been introduced into the waters of Australia have hatched and the young fish are prospering. Ice has been used in the transportation of the eggs, which, according to Mr. Youle, retards the phenomena of embryonic evolution. This gentleman has found that the vitality of the eggs may thus be preserved for three or four months. It is in this manner that eggs taken from the Rhine at Huningen in Alsace have been successfully transported to Australia. Sweden and Norway are both occupied in stocking their rivers with salmon, so that the fine example of the Zoological Society of Acclimation will not be lost.

Spontaneous generation. This interesting question is from time to time discussed by the Academy of Sciences, but without much progress being made toward a decision. Mr. Donné, a naturalist who formerly opposed the doctrine of spontaneous generation, has made some late researches which have caused him to change his mind on the question, and he has just ranged himself on the AM. JOUR. SCI.-SECOND SERIES, VOL. XLIII, No. 127.—JAN., 1867.

side of Messrs. Joly, Musset, and others, giving it as his opinion that spontaneous generation is a possible fact.

His later experiments, like those which he published an account of in 1863, were made with eggs. At that time he wrote: "The matter of which the egg is composed ought to be eminently suited to a primitive organization. I will leave the entire eggs to themselves, and when the alteration of their contents has well progressed, I will examine with the microscope the interior substance. If spontaneous generation is possible I ought to find organized beings there." The result was negative. Mr. Donné found neither mold nor infusoriæ, and he decided against spontaneous generation. Since then objections have been raised which decided Donné to resume his experiments. He reasoned thus: "The small quantity of air contained in the eggs was perhaps not sufficient to determine the phenomenon of a spontaneous generation, that is, to give life to a certain molecular arrangement of organic matter." Consequently he conducted his experiment in such a way that a larger quantity of air could have access to the eggs, the air having been previously deprived of any bodies it might hold in suspension, by passing through carded cotton. This time he obtained a generation of different kinds of mold, but found no traces of animalcules. He concludes 1st, "Microscopic vegetation may be produced at will in organic matter, left to itself, and protected from the intervention of foreign germs. 2d. Air is necessary to the development of infusorial animalcules. 3d. Air is indispensable to spontaneous generation in both kingdoms. The temperature of 30° is the most favorable to these productions."

To these conclusions the adversaries of the doctrine oppose their usual objections, viz., there were sources of error in the experiment, atmospheric germs in some way penetrated the eggs of which the shells were broken. The question thus remains still at the same point, and up to the present time it cannot be said to be experimentally resolved.

Mexican Scientific Commission.-This commission, instituted by M. V. Duruy, Minister of Public Instruction, continues its labors, which will perhaps be the only work to survive the unfortunate intervention of the French in Mexico. The commission is engaged solely with science, and may be judged of by what has formerly been said of it in this Journal, (Jan. 1866, p. 110). The third part of the second volume of its publications has appeared, containing geological papers by J. Marcou upon the frontiers between Mexico and the United States; by MM. Dolfus, Pavie, &c., upon Mexican volcanoes; and the geological sections from Vera Cruz to Mexico. Other papers are reports upon the Mexican fauna and flora, also upon the ruins of Uxmal and Mayapan, Ti-hoo and Izamal, &c.