ÆäÀÌÁö À̹ÌÁö
PDF
ePub

Five hundred and first meeting.

December 9, 1861.- MONTHLY MEETING.

The VICE-PRESIDENT in the chair.

The Corresponding Secretary read letters of acceptance from Chief Justice Bigelow, Commander J. M. Gilliss, U. S. N., Professor James Hadley, Jr., Ezra Abbot, Truman H. Safford, and Jules Marcou, who had been notified of their election into the Academy.

Professor Cooke was added to the Committee on Captain Anderson's paper, on motion of Professor Peirce.

Messrs. Peirce, Bond, Lovering, Winlock, J. I. Bowditch, and B. A. Gould were appointed a committee to wait upon Mr. Alvan Clark, and, with his consent, to examine and report upon a new and large telescope said to have been constructed by him.

Professor Peirce presented the following

Abstract of a Memoir upon the Attraction of Saturn's Ring.

The general formula for the attraction of the ring is expressed by the aid of elliptic integrals.

When the attracted point is in the plane of the ring, the formula of attraction assumes the simple form,

[merged small][merged small][merged small][merged small][merged small][ocr errors][ocr errors][merged small][merged small]

r = the distance of the attracted point from centre of ring,

P2 = the exterior radius of the ring,

P1 = the interior radius of the ring,

[blocks in formation]

When the point is very near the inner or outer circumference of the

ring, it is necessary to substitute for c2m the more exact value,

[merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][ocr errors][merged small][ocr errors][ocr errors][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small]

When the attracted point is near the plane of the ring, the attraction parallel to this plane is given by the preceding formula, and that perpendicular to the ring is given by the formula,

[ocr errors][subsumed][merged small][merged small][ocr errors][merged small][ocr errors][ocr errors][merged small][merged small][merged small][merged small][merged small]

and z = the distance of the attracted point from the plane of the ring. It appears from these formulæ, that, if Saturn's ring were one solid ring of uniform thickness, its tenacity must be sufficient to sustain, in the form of a wire, on the surface of the earth, a weight equal to six thousand miles of its own length; that is, it must be six hundred times stronger than the strongest iron wire. The demand for a strength which so immensely surpasses all experience, is a powerful argument against this constitution of the solid ring.

If the ring were subdivided into smaller rings, and if the plane of either of the secondary rings were not to pass through the centre of Saturn, this ring would vibrate back and forth perpendicular to its plane, and the whole time of oscillation would be the same as that of its revolution about the primary. The different rings would consequently have different times of vibration, so that they must constantly be in opposite phases of vibration. The average extent of vibration for all the rings could not then be materially different from the average apparent thickness of the whole ring.

The following preliminary notice of a memoir was presented :

[ocr errors]

On the Double Salts of Cyanide of Mercury, by WILLIAM P. DEXTER.

An investigation of some of the compounds of cyanide of mercury having already occupied me for a considerable time, I would beg leave to communicate the conclusions at which I have thus far arrived; and would state that I am still engaged in the prosecution of this subject.

For several of these compounds my analyses have led me to infer a composition differing from that assigned to them by previous investigators. For example, the salts of cyanide of mercury with the chlorides of nickel and cobalt, to which Poggiale* gives the formulæ

NiCl, HgCy, 6 HO,

2 CoCl, HgCy, 4 HO,

I have found to be expressed by

NiCl, 2 HgCy, 7 HO,

CoCl, 2 HgCy, 7 HO,

thus removing a difference which was certainly not to be expected in bodies so nearly related, and showing their conformity in constitution with the other salts of this class.

The salt to which Desfosses † gives the formula

KCl, 2 HgCy, HO,

I find to contain two equivalents of water; and for the analogous salt with chloride of barium, which, according to Poggiale, contains but 4 HO, I get the formula

BaCl, 2 HgCy, 6 HO;

it then agrees in composition with the corresponding salts of strontium and calcium.

The cyanide unites also with chlorides of the type R2 Cl; I have

* Compt. Rend., XXIII. 762.

† Gmelin, Handb. d. Org. Ch. Bd. I., S. 417. The original memoir in Journ. Chim. Méd., VI. 261, is not accessible to me.

formed and analyzed the compound with perchloride of iron. Its formula is

Fe, Cl, 4 HgCy, 7 HO.

I hope to get similar salts with Al, Cls, Be, Cl,, and perhaps with Cr2 Cl3.

*

For the salt of cyanide of mercury and chromate of potash, first described by Caillot and Podevin, Rammelsberg † has found the formula

2 (Ko,CrO3), 3 HgCy,

which was changed by Poggiale ‡ to

(Ko,CrOs), 2 HgCy.

An analysis of this salt has given me results agreeing very nearly with those of Rammelsberg, with the addition of one equivalent of water, which has been hitherto overlooked. Its formula would then be

2 (Ko,CrO3), 3 HgCy, HO,

The analyses of the compound which has been mentioned as consisting of

BaCl, 2 HgCy, 6 HO

have shown that the composition of this salt is not constant, and is not in exact accordance with the laws of chemical proportion. The above formula requires 16.73 Ba, and 48.77 Hg in the hundred. In the salt as I have obtained it, the barium is always deficient in quantity and the mercury in excess. The barium has been found as low as 13.4, and I have never found it higher than 15.69; while the mercury varied from 54.3 to 50.5. In general, the smaller the excess of chloride of barium in the solution from which it crystallizes, the less barium and the more mercury will be found in the salt. In some of the cases, those which gave the extreme numbers, this may very probably be owing to a mechanical admixture of cyanide of mercury, the crystals of which formed at the same time with those of the double salt, and, as I shall on another occasion show, cannot always be distinguished from them. It is possible, too, that there may be a compound

*Berzelius, Jahrsb., VI. 183.

† Pogg. Ann., Bd. XLII. S. 131, and Bd. LXXXV. S. 145.

Loc. cit.

of chloride of barium with more than two equivalents of cyanide of mercury, and that the analyses were made upon mixtures of the two salts. But the existence of such a body has never been shown, nor do we know an instance of a chloride, iodide, or bromide combining with cyanide of mercury in any other proportion than one equivalent to two. The salts of chloride of nickel and chloride of cobalt which I have mentioned, and a salt said, also on the authority of Poggiale, to be composed of

2 NHCl, HgCy,

are the only exceptions to this statement which I have been able to find. In other instances, as in that of the subjoined analysis, which was made upon large, perfectly defined, and carefully chosen crystals, deposited by spontaneous evaporation from a liquid containing a considerable excess of chloride of barium, such an explanation seems to me entirely inadmissible. The analysis gave

[blocks in formation]

A direct determination of the water upon another portion gave 6 HO = 11.63.

The above is one of thirteen analyses of this salt, and is chosen for no other reason than that the crystals were carefully selected, and that its accuracy is vouched for by the agreement of the direct determination of the water with the determination by difference. The water was determined directly in two other cases, and the variation from the determination by difference found to be less than one tenth of one per cent. To control still further the exactness of the analyses and the purity of the double salt, the chlorine was in one instance determined; the analysis gave 7.98, the quantity required by the barium present was 8.01. The cyanide of mercury used was also analyzed by the same process, and with the addition of the same reagents which had been employed in the analysis of the double salt; the result differed from the calculated composition only by one in the hundredths of a per cent. In all the analyses the deviation from the composition of the theoretical or normal salt is unmistakable, and is the more

« ÀÌÀü°è¼Ó »