loured crusts, which constitute a hitherto undescribed salt of manga

nese.

This salt dissolves readily in water, but I could not succeed in obtaining it in crystals. Its taste is sweetish and astringent, and slightly acid.

16-26 grs. of it, rendered as dry as possible by pressure between the folds of blotting-paper, and subsequent exposure to a gentle heat, were dissolved in water, and mixed with a great excess of carbonate of ammonia. The mixture was left for twenty-four hours, and during that time was frequently agitated. It was then thrown on a filter, to collect the white precipitate which had fallen. This precipitate became brown by exposure to the air, and by ignition acquired a reddish tint. In this state it was red oxide of manganese. It weighed 5.78 grs. 5.38 grs. of protoxide of manganese.

The ammoniacal liquid which passed through the filter being evaporated to dryness, and the residue redissolved in water, left a small quantity of matter, which became red by ignition, and was also red oxide of manganese. It weighed 0·07 gr. = 0·065 gr. of protoxide. So that the whole protoxide of manganese contained in 16-26 grs. of the salt amounts to 5'445 grs.

The liquid thus freed from base was treated with nitrate of silver. The chloride of silver obtained, weighed, after ignition, 0.5 gr. = 0.12 gr. of chlorine.

The excess of silver being removed by the addition of a little common salt, the liquid was precipitated by muriate of barytes. The sulphate of barytes obtained being collected, washed, and ignited, weighed 24.06 grs. 8.5 grs. sulphuric acid.

What is wanting to complete the 16-26 grs. must be water. For on other constituent could be obtained.

Thus it appears that the salt is composed of,

Sulphuric acid.....

Chlorine ..

Protoxide of manganese
Water...

8.5

0.12

5:445

2.195-16.26

The chlorine was doubtless combined with manganese, probably in the state of tris-chloride. We must, therefore, subtract 0.36 from the protoxide of manganese. The remainder, 5·085, is the quantity of manganese in combination with the sulphuric acid. Now, 5.1 is 8.5 as 4.5 to 7.5. So that the salt is composed very nearly of 1 atom sulphuric acid...... 7.5

1 atom protoxide of manganese 4.5

2 atoms water. ...

2.25-14.25

The water was rather less than two atoms. Probably a little had been driven off in the attempt to dry the salt by heat.

To what the yellow colour is owing which this salt possesses I do not know. The solution of it in water is colourless, so that none of the manganese can be in a state of red oxide. I could detect no oxide of zinc in the oxide of manganese, and none could be extracted by digesting the newly precipitated oxide in caustic potash.

Records of Science, vol. ii. p. 369.

ON CRYSTALLIZED OXIDE OF CHROMIUM. BY M. F. WÖhler. When perchoride of chromium is passed in the state of vapour, through a glass tube heated to redness, it is decomposed into oxide of chromium, which remains in the tube in a crystalline form, and a mixture of chlorine and oxygen gases. The crystals of oxide of chromium thus obtained are black, of a metallic lustre, hard, well defined, and brilliant, possessing exactly the same form as the native peroxide of iron (fer oligiste), which confirms the isomorphism before recognised in these two oxides. The exterior characters of these oxides, when crystallized, are precisely similar; the specific gravity of this oxide of chromium is 5-21, nearly approaching to that of oxide of iron; but whilst the latter gives a red powder, that of the former is green, like the common oxide of chromium. These crytals are as hard as corundum, which, next to the diamond, ranks as the hardest known body.-Journal de Pharmacie, Juin 1835.

NEW SCIENTIFIC BOOKS.

A Manual of British Vertebrate Animals. By the Rev. Leonard Jenyns, M.A., F.L.S., &c.

An Elementary Treatise on the Computation of Eclipses and Occultations. By J. W. Lubbock, Esq., F.R.S., &c.

Notices of Communications to the British Association for the Advancement of Science; at Dublin, in August 1835. Geology of Yorkshire, Vol. II. By Prof. Phillips. Philosophical Transactions, Part II. 1835.

Remarks occasioned by Lord Brougham's Paley's Natural Theology illustrated. By Thomas Martin.

METEOROLOGICAL OBSERVATIONS FOR DECEMBER 1835.

REMARKS.

Chiswick December 1. Clear and fine: cloudy and windy at night. 2. Very fine. 3. Cloudy. 4, 5. Fine. 6. Frosty and foggy. 7. Foggy. 8. Hazy: rain. 9. Cloudy and cold. 10. Slight snow. 11-13. Sharp frost. 14, 15. Hazy. 16, 17. Dense fog. 18. Clear: hail shower at noon. 19. Cloudy and cold. 20. Slight snow. 21. Overcast: clear and cold.

The quantity of

22. Sharp frost: foggy. 23-26. Frosty and foggy. 27. Cloudy. 28. Fine. 29. Overcast. 30. Fine. 31. Frosty with dense fog. rain in this month amounted only to a quarter of an inch.

P.S. Observing the discrepancy apparent in your last Journal between the results of observations at the Apartments of the Royal Society and at this Garden, I intended to have sent some account of the instruments used here, and their situation. Such will be necessary; but as some investigations are being made on the subject, I thought it better to defer it till next Number. I shall therefore only remark that the thermometers here, indicating the max. and min. of temperature, are in an open space, unaffected by radiation from buildings-a circumstance which must have a very great influence on those used for the same purposes at Somerset House.R. THOMPSON.

Boston. December 1, 2. Fine. 3. Cloudy. 4, 5. Fine. 7, 8. Foggy. 9. Cloudy: rain early A.M. 10 11. Fine. 13. Fine. 14, 15. Cloudy. 16. Fine. 17. Foggy. 18. Fine. stormy night with snow. 20,21. Cloudy. 22-26. Fine. 31. Fine.

6. Cloudy.

12. Cloudy.

19. Snow :

27-30. Cloudy.

LONDON AND EDINBURGH

PHILOSOPHICAL MAGAZINE

AND

JOURNAL OF SCIENCE.

[THIRD SERIES.]

MARCH 1836.

XXXII. On the general Magnetic Relations and Characters of the Metals. By MICHAEL FARADAY, D.C.L. F.R.S., &c.* GENERAL views have long since led me to an opinion,

which is probably also entertained by others, though I do not remember to have met with it, that all the metals are magnetic in the same manner as iron, though not at common temperatures or under ordinary circumstances t. I do not refer to a feeble magnetism‡, uncertain in its existence and source, but to a distinct and decided power, such as that possessed by iron and nickel; and my impression has been that there was a certain temperature for each body, (well known in the case of iron,) beneath which it was magnetic, but above which it lost all power; and that, further, there was some relation between this point of temperature, and the intensity of magnetic force which the body when reduced beneath it could acquire. In this view iron and nickel were not considered as exceptions from the metals generally with regard to magnetism, any more than mercury could be considered as an exception from this class of bodies as to liquefaction.

I took occasion during the very cold weather of December last, to make some experiments on this point. Pieces of various metals in their pure state were supported at the ends of

*Communicated by the Author.

It may be proper to remark that the observations made in par. 255 of my "Experimental Researches," have reference only to the three classes of bodies there defined as existing at ordinary temperatures.

Encyclop. Metrop., Mixed Sciences,' vol. i. p. 761.

Third Series. Vol. 8. No. 46. March 1836.

U

fine platinum wires, and then cooled to a very low degree by the evaporation of sulphurous acid. They were then brought close to one end of one of the needles of a delicate astatic arrangement, and the magnetic state judged of by the absence or presence of attractive forces. The whole apparatus was in an atmosphere of about 25° Fahr.: the pieces of metal when tried were always far below the freezing-point of mercury, and as judged, generally at from 60° to 70° Fahr. below zero. The metals tried were,

and also Plumbago; but in none of these cases could I obtain the least indication of magnetism.

Cobalt and chromium are said to be both magnetic metals. I cannot find that either of them is so, in its pure state, at any temperatures. When the property was present in specimens supposed to be pure, I have traced it to iron or nickel.

The step which we can make downwards in temperature is, however, so small as compared to the changes we can produce in the opposite direction, that negative results of the kind here stated could scarcely be allowed to have much weight in deciding the question under examination, although, unfortunately, they cut off all but two metals from actual comparison. Still, as the only experimental course left open, I proceeded to compare, roughly, iron and nickel with respect to the points of temperature at which they ceased to be magnetic. In this respect iron is well known*. It loses all magnetic properties at an orange heat, and is then, to a magnet, just like a piece of copper, silver, or any other unmagnetic metal. It does not intercept the magnetic influence between a magnet and a piece of cold iron or a needle. If moved across magnetic curves, a magneto-electric current is produced within it exactly as in other cases. The point at which iron loses and gains its magnetic force appears to be very definite, for the power comes on suddenly and fully in small masses by a small diminution of temperature; and as suddenly disappears upon a small elevation, at that degree.

With nickel I found, as I expected, that the point at which it lost its magnetic relations was very much lower than with See Barlow on the Magnetic Condition of Hot Iron. Phil. Trans. 1822, p. 117, &c.