The Chemist

ter may be afterwards separated from the liquid by a solution of tin, and is very little inferior to the other.

CARNELIAN. calcedony. CAROMEL. The smell exhaled by sugar when exposed to a strong heat.

A sub-species of

CARRYING POWER. If heat be applied to the upper surface of liquids, it makes its way downwards by what is called the heatconducting power of bodies, and which is found in solids as well as in fluids; but when it is applied to the lower part of fluids, these portions of them grow. specifically lighter, and rise to the top, while other portions take the lowest place, to be heated in their turn. This is called the carrying, or transporting power of fluids, and was first accurately examined by Count Rumford.

CARTHAMUS, bastard saffron, saf flower, Spanish red, China lake. A pigment obtained from the flowers of a plant cultivated in Egypt, principally for the sake of its flowers. It is used for dyeing silk of a poppy, cherry, rose, or orange red. Rouge also is prepared from Carthamus. The red colour is extracted by a solution of subcarbonate of soda, and precipitated by lemon-juice. The precipitate is dried on earthen plates, mixed with tale, or French chalk reduced to powder. The fineness of the powder and the proportion of the precipitate constitute the difference between the finer and cheaper rouge.

CARTILAGE. About one third of. the bones of animals is composed of an elastic semi-transparent solid substance, which has received the name of cartilage. It resembles coagulated albumen: it is that portion of the bones which is first formed, and in. which the earthy matters that give firmness to these organs are deposited. A deficiency of these latter, or their absorption into the system, is the cause of the disease called rickets. Ás the phosphate of lime gives bones their strength, so cartilage gives them

toughness and flexibility. Cartilage seems gradually to decrease and disappear as animals grow old.

CASE HARDENING. A process which gives to iron the hardness of steel, while it retains its own toughness. The instruments to be case-hardened are, before being quite finished, put into an iron box with powdered charcoal, and kept for a short time exposed to a strong heat, which converts the outer part into a coating of steel. The heated pieces are then immersed in water, and afterwards polished by the usual methods.

CASEIC ACID. The name given by Proust to an acid he found in cheese, and to which he ascribes some of the properties of this substance.

CASSAVA, jatropha manihat. A curious American plant, containing a pleasant food and a deadly poison. The roots are squeezed, the starch or food remains, while the juice, which separates, is used to poison arrows. Even this juice gradually precipitates starch, which is perfectly wholesome. The root itself, till thus prepared or cooked, is poisonous; but when either boiled or prepared and dried, makes a very good bread, which is used for food.

QUERIES.

To the Editor of the Chemist. SIR,-Observing in No. XXV. of your interesting little Work, the communication T.Z. on a method of decomposing water by means of galvanic electricity, I should take it as a favour if you or your Correspondent would answer the following Query. Does the decomposing power of the galvanic battery depend on the size of the plates or on the number of series? Your Correspondent gives a description of a simple apparatus for collecting the gases in a separate state; I take the liberty of inclosing another more complex, but very convenient, which, if it meets your approbation, you may, perhaps, insert in a future Number. I remain,

Your obliged, &c.

J. R. S.

SIR, Permit me to ask the best method of obtaining the gold from washings which are produced from old frames or other gilt work, in the business of carving and gilding (as it is usually called, to distinguish it from water-gilders.) The mode of proceeding with work which is to be regilt, is to wash the old gold off with a piece of cloth and water; it is then put in a pan, and when settled, the water is poured off, leaving the dischargings behind, which are dried and sold; but many pounds have been thrown away for want of knowing how to extract the gold from it. If, Sir, you will inform me the best me thod, by any chemical or other process, you will much oblige a constant reader of your paper. Yours, most obediently, In the dark, OLIVER

Sept. 1st.

HEAVY AND LIGHT WATER.

TAKE two portions of the same water, and colour each of them differently, by means of any two of the substances mentioned at page 397 of the Chemist. Let one of these portions be heated while the

other remains cold. If the hot water be then poured gently into a glass jar containing the cold water, it will remain on the surface and scarcely mix with the cold water; but if the cold water be poured on the hot it will sink to the bottom of the vessel; showing, that the specific gravity of the same body may be decreased or increased by the effect of heat.

TO CORRESPONDENTS.

The present Number completes the First Volume of The Chemist, and it was consequently our intention to publish a Supplemental Number next week, containing the Index, Preface, &c., weeks, from being unable to get the but we are obliged to delay it for a few engraving ready with which the Supplement is to be ornamented.

The communication of James Wright has been received, and will be inserted in our next.

Juvenis is informed that we do not consider the Bible to be authority in matters of science. Every theory, either of light or of any other phenomenu, must be substantiated by facts». before it can be described as incontestibly proved. The passage which he quotes has given rise to a vast deal of decided as to its meaning. He will see, discussion, and philologists are not yet therefore, we should suppose, at once, the inutility of framing a theory of the whole universe on an obscure phrase in a book which is admired from our being unable to comprehend it. This will, we hope, be a satisfactory reason why we do not insert his letter. At the same time, we agree with him, that no ques→→ tions which are not plainly above the power of man to solve should ever be regarded as excluded from our researches.