to separate manganese in solution from other substances with which it is in combination, as has been proposed by some chemists, is therefore in the highest degree improper. When water containing the greatest possible quantity of carbonate of manganese in solution is exposed to the air, it can hardly be said to cover itself with a skin. This erroneous opinion has probably originated from confounding manganese with magnesia. When a solution of manganese in an acid (the acid being in excess) is decomposed by a carbonated alkali, and the filtered liquid is diluted with water, if it be left exposed to the air, or placed in an artificial warmth, it is soon covered all over with a thin skin; but it is impossible from this to estimate the qualities of carbonate of manganese, or to conclude its great solubility in carbonic acid water; for when this skin is accurately examined, we find that it is a salt composed of carbonic acid, oxide of manganese, the alkali employed in producing the precipitation, and probably of the acid likewise in which the metal was previously dissolved.

In order to precipitate manganese completely from a solution, it is necessary that there should be no excess of acid present. Only the neutral solutions are completely decomposable.

The fat oils dissolve carbonate of manganese by the application of heat, and form with it a compound having the consistence of plaster. This observation was first made by Scheele.

Estimate of the Proportion of the Constituents of Carbonate of Manganese.

I first estimated, by dissolving a hundred grains of carbonate of manganese, the loss of weight sustained by the escape of carbonic acid. By this method I determined the proportion of acid to amount to 34 25 per cent.

To determine the other constituents, I filled a very small good coated retort with carbonate of manganese, of which 120 grains were requisite. The beak of the retort passed into a glass ball, from which proceeded a tube to allow the gas to escape. By the application of a heat, at first gentle, but gradually so high as to make the retort red-hot, the gas and the water were expelled from the salt. After continuing a red heat for two hours, the apparatus was taken to pieces, and the weight of the different products obtained determined. The. water in the glass ball weighed 12 grains; and the oxide remaining in the retort, and which had acquired a greenish grey colour, weighed 67 grains.

If we subtract the weight of the oxide and water thus obtained from the 120 grains employed in the experiment, there remains a loss of 41 grains. As the gas which made its escape during the distillation was pure carbonic acid, this loss gives us 41 grains for the amount of that acid in the salt. This agrees very

nearly with the result of the first experiment, according to which 100 grains of carbonate of manganese contain 34.25 grains of carbonic acid.

One hundred grains of the salt are composed of the following constituents:

The greenish grey oxide thus obtained dissolves in acids without the extrication of any gas, and the same compound is obtained as would have been got by the solution of the carbonate in the same acid. Hence it is to be looked upon as the real base of the salt; and the white powder, which appears when manganese is precipitated by an alkali, must be considered as a hydrate, or an oxide still combined with a portion of acid.

V. Action of Sulphuric Acid on Manganese.

(A.) On the metal. The action of concentrated sulphuric acid upon manganese in the metallic state is very inconsiderable. It produces some heat, and a small portion of the metal is dissolved. Several chemists, it is true, are of opinion that the solution takes place very readily; but I conclude, upon very good grounds, that the regulus which they employed was not quite in the metallic state, but contained some oxygen combined with it. When the acid is diluted with water, heat is evolved, and hydrogen gas disengaged, which has a very peculiar smell, similar to that of asafoetida. This smell is probably owing to a portion of the metal being carried off in solution in the gas. During the solution the liquid assumes a green colour, which disappears when the acid ceases to act upon the metal. This appearance probably depends upon the formation of green oxide, as when carbonic acid acts upon the metal.

The concentrated solution has a light rose-red colour; and when it is diluted with water, the colour becomes insensible. have never been able to procure colourless crystals from this colourless solution. Indeed, as the metal which is oxydated at the expense of the water gives at first a coloured liquid, it is not reasonable to expect colourless crystals of sulphate of manganese.

190 grains of concentrated sulphuric acid, of the specifie gravity 1.860, required for neutralization 100 grains of metallic manganese. The filtered solution (which left grains of black, brilliant, minutely divided charcoal,) gave, when decomposed

by carbonate of ammonia,* 205 grains of carbonate of manganese dried at the temperature of 80°.

From this experiment it follows, that 100 parts of carbonate of manganese consist of

(B.) On the protoxide. -Both the pure protoxide and the carbonate of manganese dissolve completely in sulphuric acid, in whatever state of concentration it be. The solution has the same properties as that mentioned in the last paragraph, and what I now say of it may, to save repetition, be applied to both.

When the neutral solution is rapidly evaporated, the sulphate of manganese separates in the state of a granular powder, or embryo crystals; and no crystals are obtained during the cooling of the liquid. To obtain this salt in the state of regular crystals the saturated solution must be left to spontaneous evaporation. I gained the same object more speedily by means of some crystals of sulphate of manganese, which I introduced into a solution concentrated, as far as possible, by rapid evaporation. I then placed the solution for farther evaporation upon the top of a stove, where the temperature was between 68° and 73°. By this contrivance I reduced the whole salt, without exception, to a regular state.

The crystals of sulphate of manganese which first shoot are of a faint rose-red colour. The last crystals have a white colour, and contain a great excess of acid.

Properties of crystallized Sulphate of Manganese.

It crystallizes, 1. In very broad flat four-sided prisms, either complete or slightly truncated on the alternate edges of the sides. The crystals are usually more or less intermixed with each other, and hence incomplete. 2. In rhombs.

The crystals are completely transparent, have a light rosered colour, and a bitterish metallic taste.

At the temperature of 55° they remain unaltered in the air, and do not attract more oxygen even when left in contact with oxygen gas. At the same temperature, 2 parts of water dissolve one part of the salt. They are insoluble in alcohol.

I always took care to convince myself by repeated experiments that no oxide remained in solution in the liquid.-J.

Their specific gravity amounts to 1.834, that of water being

1.000.

At the temperature of 66° they become opake and white.

When the crystals are heated to redness in a coated retort, they lose their water of crystallization, and a white dry mass remains in the retort, which dissolves in water by the assistance of heat. When the fire is raised so high as to melt the retort, an imperfect decomposition of the salt is obtained. Sulphurous acid is disengaged, and some glaceous sulphuric acid is found in the receiver. There remains in the retort a mixture of sulphate of manganese, and of brown oxide.

The aqueous solution of sulphate of manganese is neither precipitated by oxalate of potash nor borate of soda. Some chemists, indeed, have obtained a precipitate by means of this last salt, consisting, as they say, of borate of manganese; but this only happens when the borate used contains an excess of alkali, as is the case with the borax of commerce. Pure tartaric acid produces no precipitate in this solution. When the liquid into which this acid has been poured is evaporated sufficiently, prismatic crystals make their appearance, which have the properties of sulphate of manganese. Infusion of nutgalls, and the alkaline chromates and arseniates, produce no change upon the solution of sulphate of manganese.

The solution is precipitated by the alkaline prussiates, carbonates, and phosphates, and a white powder is obtained, consisting of the oxide of manganese united with the acid of the salt employed. If the sulphate of manganese contains the smallest portion of copper, the precipitate formed by the action of an alkaline prussiate has a peach-blossom red colour.

Estimate of the Proportion of the Constituents.

One hundred and fifty grains of the salt were dissolved in water, and decomposed, while hot, by means of muriate of manganese. The sulphate of barytes which separated was carefully collected, washed, dried, and heated to redness. It weighed 148 grains. As it appears from Klaproth's late experiments that the proportion of acid in dry sulphate of barytes amounts to 34 per cent., it follows that 148 grains of the salt contain 50 grains of acid.

The solution of manganese thus freed from sulphuric acid was precipitated by means of carbonate of potash. The precipitate, collected, washed, and dried at the temperature of 80°, weighed 834 grains, which, from the preceding experiments on the composition of carbonate of manganese, indicate 46 grains of protoxide.

As the 53 grains of loss must be imputed to the water con

tained in the salt, it follows that 100 parts of sulphate of manganese consist of the following constituents :-

Sketch of the present State of Agriculture in Berwickshire. By the Rev. J. Thomson, Minister of Eccles, in that county.

(Concluded from Vol. I. p. 265.)

FALLOWING.-In Berwickshire the following mode of fallowing is usually employed. As soon after harvest as possible the land that is to be fallowed receives its first furrow, or ploughing. Care is taken that in clay lands the ridges be sufficiently high, that the water may run off into the furrows which are opened by the plough and spade, that it may thence discharge itself into the ditches which surround the inclosure. This first ploughing is considered as of great utility. It buries the stubble, and thus tends to convert it into vegetable soil. It leaves the field in as dry a state as possible; and the winter frosts pulverize the soil. This ploughing is generally made as deep as possible, because the plough, on account of the softness of the soil, can then easily penetrate to the proper depth. Thus, also, the future ploughings are rendered easier.

The second ploughing is seldom given till the oats be sown, and sometimes also the barley. If the land abound with weeds, such as couch-grass, and the season be dry; then it is well harrowed, and the couch-grass is gathered by the hand, and laid up in heaps. These heaps are afterwards led off the field, and mixed with lime, or lime and stable manure, and thus form an excellent compost. It is of great advantage that couchgrass should be gathered as early in the season as possible before it begins to grow, because it can be done both more easily and more completely when the soil has been pulverized by the winter frosts than afterwards: but if the season be wet, the land cannot be sufficiently harrowed, nor the couch-grass gathered, till the third ploughing.

The third ploughing takes place when it is supposed all the