greater celebrity, afterwards discovered the same substance in a mineral called red shorl. He called it titanium, and this name is now adopted. M. Laugier describes it as of a yellow colour, having considerable lustre and elasticity, and as being very difficult to fuse. It is considered a very intractable substance, and nothing more of the least importance has been learnt concerning it.

A substance to which Berzelius has given the name of selenium, has been obtained by him from the residuum of some iron pyrites, which are made use of at Fahlun, in Sweden, to obtain sulphuric acid. It is a brown substance, with a metallic lustre; is easily melted, and then remains for a long time in a soft state, so that it may be kneaded, and even drawn into threads. High authority places it among the metals simply on account of its lustre, but this can scarcely be sufficient reason; and if, after being more closely examined, it should be found to be a peculiar undecompoundable substance, it will most probably be classified under some other head. It first excited curiosity, and is still distinguished, by emitting a smell resembling that of horse-radish.

Osmium is the other metal which Mr. Tennant discovered when he was making his experiments on the ores of platinum, which have been already mentioned in speaking of palladium and iridium. Its oxide gives out a certain smell resembling the odour of chlorine. The metal, if it deserves the name, is of a dark grey or blue colour, and evaporates with the above smell in the open air when heated. When kept in close vessels, so that its oxidizement is prevented, it does not appear volatile; and when subjected to a strong heat underwent no apparent alteration. This substance has only been obtained in very minute quantities, and its properties are yet very imperfectly known.

DICTIONARY OF CHEMISTRY.

BLEACHING POWDER, bleaching. salt, chloride of lime.

BLENDE. An ore of zinc. BLOOD always separates into two masses, one a thick substance, called crassamentum, or cruor,. and the other called serum, the latter being in general in proportion of 3 to 1 of the former. 1000 parts of serum of human blood are said to consist of 905 water, 80 albumen, 6 muriate of soda and potash, 4 lactate of soda with animal matter, and 4.1 of soda and phosphate of soda with animal matter. The cruor consists of 64 colouring matter, and 36 fibrina in 100.

BLOOD STONE. A species of calcedony has this name.

BLOW-PIPE. A well-known in

strument, of which there are several kinds. Formerly it was only used by the brazier or goldsmith; now it is one of the most useful instruments possessed by the chemist.

BLUE CARBONATE OF COPper, mountain blue, blue calyx of copper. An ore of copper, frequently met with in Britain.

BLUE IRON EARTH, native Prussian blue. An iron ore, containing a considerable quantity of phosphoric acid.

BLUE, PRUSSIAN, consists of oxide of iron and ferro-prussic acid.

BLUE SAXON. Indigo and sulphuric acid; some persons add potash.

BOLETATES. Salts composed of a base and boletic acid.

BOLETIC ACID. A vegetable. acid, discovered by M. Braconnot in 1811, of which little is known.

BOLETUS. The species of mushrooms in which it was detected.

BOLOGNA STONE, bolognian stone, ponderous stone, native sulphate of barytes. A phosphoric stone.

BONES Owe their strength to the presence of phosphate of lime, which is kept united into a mass by animal gelatine. When calcined, human bones consist of, in 100 parts, 81.9, phosphate of lime, 3: fluate of lime, 10 lime, 1.1 phos

phate of magnesia, 2 soda, 2 carbonic acid. Before calcination they probably contain about the half of their weight of gelatine, but the proportions vary.

BORACIC ACID. The acid found in borax. It is also found on the edges of some hot springs near Sapo, in the Florentine dominions.

BORACITE, borate of magnesia. BORATES. Salts formed with boracic acid and a base.

BORAX, borate of soda, consists of 36 boracic acid, soda 17, water 47. It is well known as an excellent flux, and is employed in many arts. BORON. The elementary base of boracic acid. A simple substance. BOTANY BAY RESIN exudes spontaneously from a tree in New Holland.

BOULDERS, boulder stones. Rolled blocks of granite, found in several parts of Europe at a great distance from any granite mountains. To account for their existence in such places has given birth to several geological theories.

DISTILLATION.

Art. I.

WE mean, in a series of papers under this title, to present our readers with a short account of the principles and of the practice of distillation, more particularly, however, of that part which is usually understood by the term, or the manufacture of ardent spirits. It is a well established fact, that almost all substances require a different quantity of heat to make them assume the form of vapour, and consequently when any compound substance consists of ingredients that are volatilized by different quantities of heat, we are able to separate them from one another.

We

have already given several examples of this. The mode in which mercury is separated from gold and silver is one in point; and this separation is effected by the mercury passing over in vapour at 6509 Fahrenheit, while the other metals will not, at that temperature, assume a liquid form. If the substance which remains be the

most precious, and if the process is undertaken only for its sake, it is called purification; if, on the other hand, it is the substance which flies off earliest which is most precious, and it is for its sake that the process is undertaken, it is called distillation. Thus, when water impregnated with carbonic acid gas and air is made to boil, the whole of the carbonic acid gas and air are made to pass off, and the water is said to be purified; but if, after the carbonic acid is expelled, the process is continued, and the steam or vapour of water, as it rises, is again condensed and preserved, this water is said to be distilled, and the process is called distillation. This theory, or rather definition, of distillation supposes, how truly we will not decide, that the products of distillation all preexisted in the compound substance subjected to the action of the fire, and that no new substance is generated by this action. Thus Messrs. Brande and Gay Lussac have both proved, by very decisive experiments, that brandy or alcohol exists, ready formed, in all wines; and they have pointed out a method by which it can be separated, by means of chemical affinities, in as pure a state as if it had been distilled. We do not ourselves go the whole length of this theory; and we suppose there are many cases, that, for example, of the distillation of pyrolignous acid, in which the action of heat in the close still first disposes the elementary substances to take a new form, or a new combination, and then expels the new formed substance. This distinction should certainly not be overlooked in practice. When the substance to be obtained exists ready formed, we have only to attend to the means of most completely separating it. When it does not exist ready formed, it is plain there is another important matter demanding attention.

The principle is the same, whether the substance on which we are to operate be solid, as wood and bones, or liquid, like wort or wine; or whether the substance we are to

obtain be a fluid, like brandy, or a solid, like sulphur. In the former case a different kind of still is only necessary: in the latter the condensing apparatus must be very different. If the substance to be obtained condenses into the solid form, like corrosive sublimate or sulphur, nothing more seems necessary than to convey the vapour into a vessel where it is deposited. In such cases, too, the vapour adheres to the upper part of the still or alembic in which the process is carried on, and then it is called not distillation, but sublimation. It is more common, however, to place another vessel inverted over the still, for the reception of the sublimated products, or, as in the manufacture of sulphur, to convey the vapour into a room constructed for the purpose. The substance is then condensed on the inside of the vessel or room, and is scraped off, or removed in the form of a cake; and in this way several chemical products in common use are obtained. If the vapour condenses into a liquid, the condensing part of the process is the most important; and instead of a vessel simply inverted over the still, a more complicated apparatus is necessary. The nature of this depends in some measure on the circumstance, whether the vapour is to be speedily or slowly condensed. Generally it is desirable to condense it speedily; it saves time, which is a saving of expense; it saves space, and it also saves the cost of a long line of condensing tubs, or other apparatus. As the first part of the process consists in making the substance it is desired to obtain separate, by means of heat, from other. substances, in the form of vapour; so the second part of the process consists in again abstracting this heat, and reducing the desired substance to the form of a liquid or a solid. The natural tendency there is in heat equally to distribute itself in all bodies, insures us an easy means of abstracting the heat from the vapour, by merely allow ing the vessels in which it is contained to be freely exposed to the

contact of air. This does not, however, work quick enough for man, and he hastens the condensing process by a variety of methods, but chiefly by the application of cold water. It would be an almost endless task for us to describe every one of these methods. It seems that we have done sufficient in stating the principles; and are quite sure that our intelligent readers will know how to apply them. Generally we may observe, that the condensing part of the process has not been so much improved as the vaporizing part. We believe, for example, the combined effects of both air and water are not efficaciously brought into action. Thus, in general, the cooling agency of water is only applied, as in the apparatus for condensing pyrolignous acid, and, as in the tubs which surround distillers' worms, excluded from the cooling agency of renewed currents of air. In many parts of Europe, spontaneous evaporation, by spreading salt water over a large surface, is employed to concentrate the water, which produces a considerable degree of cold; and we do not see why some similar process should not be adopted by the distiller; why, for example, the surface of the condensing apparatus, or of the worm, should not be exposed to a current of air, while it is also kept constantly wet, by water dripping on it, or running over it.

From this outline of the principles of distillation, it will be evident to our readers, that it is a very general process, subject, indeed, to many subordinate details. It is probably, also, a very ancient art, for it is taught man by nature, whenever he will open his senses to her instruction. The sun during the day separates water from the surface of the earth, and spreads it as vapour through the atmosphere; as his heating powers are diminished, this vapour condenses of itself, and again separates from the air in the form of dew. This is a perfect species of distillation, and dew, unless contaminated by

that on which it falls, is found to be pure or distilled water. For many purposes this distilling power of the sun is taken advantage of in the arts, and a process called distilling by the sun is still carried on in warm climates. With this example of nature under their eyes, we have reason to believe men would not be very long before they began to imitate it; and accordingly, distilling, in the enlarged sense of the word, is a very ancient art, and is now very generally known. At least, men were acquainted with it wherever the civilization of the ancient world reached, and now are wherever civilization is diffused. The distillation of ardent spirits, indeed, is said not to have been known in Europe till towards the year 1150, when it was introduced into Spain by the Moors. Although the Grecks and the Romans knew some distilling processes, there is no evidence that they were acquainted with what we more particularly call distillation.* But at present, from that part of Asia where man and the arts are both supposed to have had their origin, to the most northern point of Europe, hence to the most southern cape of Africa, and throughout the vast continent of America, the knowledge of distillation has been spread, and the art is now practised. We believe, after cultivating the ground, building habitations, and making clothes, distillation is the most generally practised of all the useful arts, and exists as a trade where the art of making leavened bread is yet unknown. We are quite persuaded, that vices and miseries are, if we may so speak, only exceptions to the great system of nature, and whatever is general, or almost universal, cannot be evil. Should the surly moralist reproach distillation with the excesses sometimes committed by its aid, we will point his attention to the beneficial effects of ardent spirits in enabling the constitution of man to resist

*See Anderson's History of Commerce, vol. i. p. 83.

the noxious effect of marsh miasma. Without them it may be doubted if he could ever have drained the marshes of Holland, now a memorial of human skill and human power, far more ennobling than the pyramids of Egypt; or ever have cleared the woods and savannahs of America, which promise, as greater freedom seems there destined to raise up a more powerful community than the world has ever yet seen, hereafter to exhibit something which shall far surpass both the dykes of the republican Dutchmen, and the tombs of the Egyptian kings. If any morose cynic should still think these memorials, and these triumphs, and the sparkling joys of incipient intoxication, mere trifles compared to the evils of inebriety, we should still say he took only an imperfect view of the great process of distillation; and we would ask him how he could possibly condemn that for which he is indebted for dew and rain in nature, and for so many things in art that we are at a loss which to

select as the most useful and valuable.

As in Great Britain little or no spirits is distilled without one portion of the grain having first been malted, we shall in our next paper on this subject describe the process of malting.

'ANIMAL HEAT.

To the Editor of the Chemist. SIR,-It occurred to me, in reading in No. XXI. the Article on Animal Heat, that the theories hitherto started are by no means irreconcileable; and that the opi nions of Edwards and Brodie are only two different views taken of the same fact from opposite points, but are themselves equally correct. Admit with Edwards that oxygen is, in the process of respiration, absorbed by the arterial blood, of which one of the component parts is carbon, it does not follow that a decomposition of the venous blood, by the separation of part of its