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neither of these are in the requisite proportions. The escape of the acid by heat seems to indicate the presence of a portion of water amounting to about two-thirds of the loss stated as sustained in the analysis.

II. Polychroite.

This is the name given by Bouillon Lagrange, and Vogel, to the colouring matter of 'safron, formerly considered by chemists as extractive, but which they conceive to be a peculiar vegetable principle. To obtain it, we have only to digest saffron in water, evaporate the liquid to the consistence of a thick syrup, and digest this residue in alcohol. When the alcohol is evaporated, polychroite remains behind in a state of purity. The properties of this substance are as follows:

1. It has a very intense yellow colour. Its taste is bitter, similar to that of saffron, and it has an agreeable smell.

2. It dissolves readily in water and alcohol, but scarcely in ether, and not at all in fat and volatile oils.

3. When the solution of polychroite is exposed to the light, it gradually loses its colour. Its colour is destroyed likewise by oxymuriatic acid. The addition of a few drops of sulphuric acid changes its colour to an intense and beautiful blue. Nitric acid, added in like manner, renders it green.

4. It combines with lime, potash, and barytes, forming with these bases soluble and insoluble compounds.

5. When sulphate of iron is dropped into a solution containing it, a dark brown precipitate is formed.

6. It stains cloth of an intense yellow colour.

7. When distilled it yields an acid liquid, a yellow coloured oil, and carbonic acid gas, and carbureted hydrogen gas., The acidulous liquid contains ammonia. The charcoal, when incinerated, leaves traces of carbonate, sulphate and muriate of potash, of carbonates of lime and magnesia, and of iron. See Ann. de Chim. vol. lxxx. p. 198.

III. Picrotoxine.

This is the name given by M. Boullay to a peculiar substance which he extracted from the Cocculus Indicus, to which that body owes its deleterious qualities. Picrotoxine may be obtained by the following process. Boil the seeds deprived of their pericarp in a sufficient quantity of water. Filter the decoction, and precipitate it by acetate of lead. Then filter again, and evaporate slowly to the consistence of an extract. Dissolve this extract in alcohol, and evaporate the solution to dryness. Repeat these solutions in alcohol and evaporations, till the residue is wholly soluble in alcohol and water. It then consists of picrotoxine mixed with a little colouring matter. Agitate it with a

very small quantity of water, the colouring matter is dissolved, and the picrotoxine separates in small crystals. Its properties are as follows:

1. Its colour is white, and it crystallizes in four-sided prisms. 2. Its taste is disgustingly bitter.

3. A hundred parts of boiling water dissolve four parts of picrotoxine, one half of which separates as the solution cools. The solution does not alter the colour of vegetable blues.

4. Alcohol of the specific gravity 0-810 dissolves the third of its weight of this substance. A little water throws down the picrctoxine; the addition of a greater quantity redissolves the precipitate.

5. Sulphuric ether of the specific gravity 0·700 dissolves only 0.4 of picrotoxine.

6. It is insoluble in oils, both fixed and volatile.

7. Diluted sulphuric acid does not act upon it; concentrated acid dissolves it, assuming a yellow colour. When heat is applied, the picrotoxine is charred and destroyed.

8. Nitric acid dissolves it without the disengagement of nitrous gas. The solution is yellowish green. When heat is applied, the picrotoxine is converted into oxalic acid; but about 18 parts of nitric acid are requisite to produce this effect.

9. Muriatic, oxymuriatic, and sulphurous acids, have no action on it.

10. Acetic acid dissolves it readily. Carbonate of potash precipitates it from this solution unaltered.

11. Potash, soda, and ammonia, diluted with ten times their weight of water, readily dissolve picrotoxine.

12. When triturated with potash, it assumes a yellow colour, but does not emit the odour of ammonia.

13. When heated, it burns without melting, or giving out flame, exhaling a white smoke, which has a resinous odour.

14. When distilled, it yields very little water and gaseous products, but much yellow coloured empyreumatic oil, and a brilliant bulky charcoal remains behind. See Ann. de Chim. vol. lxxx. p. 209.

IV. Boletic Acid.

This is a new vegetable acid obtained by Braconnot from the juice of the boletus pseudo-igniarius by the following process. The juice was boiled, filtered, and evaporated cautiously to the consistence of a syrup. This syrup was repeatedly digested in alcohol, the insoluble portion was dissolved in water, and preci pitated by nitrate of lead. The white precipitate thus obtained was mixed with water, and decomposed by sulphureted hydrogen gas. The water being now evaporated yields numerous crystals,

which constitute boletic acid. The properties of this acid are as follows:

1. When purified by solution in alcohol and crystallization it is white, not altered by exposure to the air, and consists in irregular four-sided prisms.

2. Its taste is similar to that of tartar; it requires 180 times its weight of water to dissolve it at the temperature of 68°. It is soluble in 45 times its weight of alcohol

3. The aqueous solution reddens vegetable blues. Nitrate of lead occasions a precipitate in it which is redissolved by agitation. It precipitates the red oxide of iron completely from its solutions in the form of rust coloured flocks; but it does not throw down the black oxide of this metal. It precipitates nitrate of silver in the state of a white powder, which is soluble in nitric acid. Nitrate of mercury is precipitated in the same state; but the solution dissolves with difficulty in nitric acid. Neither lime nor barytes water produce any effect upon the aqueous solution of this acid.

4. When heated it rises in white vapours, which irritate the throat, and condense on surrounding bodies in the form of a farinaceous powder, When distilled the greatest part of it sublimes unaltered, excepting that it afterwards crystallizes more regularly. At the same time a little liquid appears, having a strong smell of acetic acid.

5. Boletate of ammonia is a salt which crystallizes in flat four-sided prisms, and is soluble in 26 times its weight of water at the temperature of 68°. Its taste is cooling, saline, and somewhat sharp. When heated it melts, swells, and sublimes. It precipitates red oxide of iron; but does not alter sulphates of lime, alumina, or manganese. It slowly precipitates nitrate of copper in blue silky needles.

6. Boletate of potash is very soluble in water, and crystallizes with difficulty. Acids precipitate the boletic acid from it. 7. When boletic acid is heated with carbonate of lime it dissolves it with effervescence. The boletate of lime crystallizes in flat four-sided prisms. This salt has little taste, and requires at least 110 times its weight of water, at the temperature of 72.5°, to dissolve it. It is decomposed by oxalic and sulphuric acids,

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8. Boletate of barytes is an acidulous salt in white plates, little soluble in water or nitric acid. When thrown on a red-hot it burns

littledly, with a red flame, and striking scintillations,

leaving for residue carbonate of barytes.

9. When heated with iron filings and water, hydrogen gas is emitted, and a yellow liquor is obtained with an inky taste. See Ann. de Chim. vol. lxxx. p. 272. povra

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A correspondent informs me that the process followed by Mr. Hutton to freeze alcohol, and which he thought proper to conceal, was as follows. The alcohol is put into a condensing vessel, and air condensed on it as far as can be done with safety. The vessel is then reduced to as low a temperature as possible by means of freezing mixtures, and the air being allowed suddenly to make its escape increases the cold so much that the desired effect is produced.

VI. Situation of Cryolite in Greenland.

I received from Mr. Allan the following correction of his account of Greenland from Mr. Giesecké too late for insertion in the last Number of the Annals of Philosophy:

Cryolite occurs in two small detached beds, resting on gneiss; one of them is composed entirely of the fine white cryolite uncontaminated with any mixture; in the other, the brown variety occurs mixed with galena, pyrites, &c. They are situated very near each other. The first is touched at high water by the tide. It varies from 1 to 24 feet in thickness. From the decompositions which this curious mineral has undergone, it could not be procured attached to the rock on which it rests. It is, besides, divided from it by a thin layer of mica, always in a state of disintegration. Mr. Giesecké is inclined to consider the cryolite as belonging to a floetz formation.”

VII. Meteorological Apparatus.

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In answer to the correspondent who wishes for correct information respecting Mr. Luke Howard's meteorological apparatus, I have only to refer to the wrapper of Number II. of the Annals of Philosophy, where every thing respecting it with which I am acquainted has been noticed. As to evaporation, he will find useful observations on it in Saussure, and in a paper by Mr. Dalton published in the Manchester Memoirs. The part of the apparatus most frequently wrong is the rain-gage, which never can give correct information unless it be placed within a few feet of the ground, and detached from all buildings. I believe the mean temperature indicated by the thermometer in most journals is too high. It must always be so, unless the lowest point to which the thermometer falls in the night be marked. This, in summer, is usually about sun-rise; in winter, it is irregular, depending on the wind. A good Six's thermometer I conceive to be a necessary appendage to every meteorological apparatus.

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VIII. Biddery Ware.bs
I have been favoured by Dr. Wilkins with the following

receipt, which he informs me is followed in making Biddery ware in some parts of India:

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Melt all these together; take 3 ounces of the alloy, and melt them with 16 ounces of zinc. This mixture constitutes the alloy of which Biddery ware is made. To give it a black colour, wash the surface with a solution of 1 oz. of sal ammoniac, 4 oz. of saltpetre, oz. of common salt, oz. of blue vitriol, and dip the Biddery ware into this solution.

IX. Gong.

The

Gongs are manufactured in Canton in an open manner. largest kinds are made in one of the interior provinces of China, They are not made in any part of India.

ARTICLE XIII.

List of Patents.

JOHN BRAZILL, of Great Yarmouth; for a machine for working capstans and pumps on board ships, which machine may also be applied to various other useful purposes. Dated September 4, 1813.

JOHN WESTWOOD, of Sheffield; for a new method of embossing ivory by pressure. Dated September 9, 1813.

FRANK PARKINSON, of Kingston-upon-Hull, distiller; for a still and boiler for preventing accidents by fire, and for preserving spirits and other articles from waste in the operation of distilling and boiling. Dated September 4, 1813.

HENRY LISTON, Minister of Ecclesmachen, Linlithgow; for certain improvements on the plough. Dated September 23,

1813.

HENRY OSBURN, Whitmore-house, Warwickshire; for a method of making tools for tapering of cylinders of different descriptions, made of iron, steel, metal, or mixture of metals; and also for tapering bars of iron, steel, metal, or mixture of metals. Dated October 15, 1813.

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ROBERTSON BUCHANAN, Glasgow, civil engineer; for certain improvements in the means of propelling vessels, boats, barges, and rafts, which may also be applied to the moving of water wheels and wind mills, the raising of water, the dredging, cleansing, or deepening of rivers and harbours, and the impelling of other machinery. Dated October 18, 1813,

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