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When the basis of potash is dropt into water, an instantaneous explosion takes place, and a white ring of smoke often ascends, which gradually expands as it rises in the air. When the basis of potash is presented to water without the contact of air, the decomposition is rapid, much heat and noise is produced, but no luminous appearance takes place. The liberated gas is hydrogen. On ice the base of potash takes fire, with a bright flame, and a deep hole is formed, which contains a solution of potash. When a globule is, placed upon moistened turmeric paper, it takes fire, and moves along rapidly as if in search of moisture,' leaving behind a deep reddish brown trace, which, like dry caustic potash, destroys the texture of the paper. When the base of potash is presented to alcohol or ether, it decomposes the small quantity of water contained in these fluids. In ether this decomposition presents an instructive result. As potash is not soluble in this fluid, when the basis is thrown into it, the new formed alkali, as fast as it absorbs oxygen, renders the ether white and turbid. When the basis of potash is brought into contact with solutions of the mineral acids, it takes fire and burns on the surface with flame. When it is immersed beneath the surface of sulphuric acid, it becomes covered with a white saline substance, assumes a yellow coating, and disengages a gas, which has the odour of sulphureous acid. From nitrous acid, nitrous gas is disengaged, and nitrate of potash is produced. The base of potash combines with the simple inflammable bodies, and with metals. The compounds are similar to the metallic phosphurets and sulphurets. When it is brought into contact with a piece of sulphur, and pressed upon, a violent action takes place, and the compound produced is phosphate of potash. When this union is effected under naphtha, no elastic fluid is evolved, the product is of a lead colour, and when spread out possesses a metallic lustre. This sulphuret has a considerably higher fusing point than its two constituent parts, remaining soft and solid in boiling naphtha. On exposure to air it becomes decomposed, and forms phosphate of potash; when heated it emits fumes, but does not take fire till the temperature is raised to ignition.

When the basis of potash is made to combine with sulphur, in tubes filled with the vapour of naphtha, the combination is effected rapidly, and is accompanied by heat and light The product is of a grey colour. It strongly acts on the glass, and acquires a brown tint. In tubes hermetically sealed, no disengagement of gas takes place; but when the experiment is made in a tube connected with the mercurial apparatus, a small portion of sulphuretted hydrogen is evolved.

When the union with sulphur is accomplished in the open air, a rapid inflammation takes place, and sulphuret of potash is formed. The sulphuretted base is gradually oxygenised on exposure to the air, and sulphate of potash is produced. Quicksilver readily combines with the base of potash, and much heat is set free during this union. When one part of the base is added to eight or ten parts in bulk of mercury, at a temperature of 60", the compound greatly resembles mer. cury. If a globule is made to touch a globule of mercury of twice its volume, the product, when cold, is a solid metal, similar in colour to silver. If the basis is about th of the weight of mercury, the amalgam possesses a still greater degree of hardness and becomes brittle. When these amalgams are exposed to air they are again decomposed; they rapidly absorb oxygen, potash is reproduced, and in a few minutes the mercury again separates in its metallic state.The amalgam of the base of potash and mercury rapidly decomposes water, by mere contact, with a hissing noise; hydrogen is set free, potash formed, and the mercury separated. The fluid amalgam of mercury and the base of potash alloys with all the metals, even with iron and platina,

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The base of potash combines with gold, with silver, and with copper, when heated in close vessels. These alloys decompose water, potash is formed, and the metals separate in an unaltered state. The base of potash, with fusible metal, forms a less fusible compound.

The action of the basis of potash on oily and other inflammable compounds, confirms the evidence of the great strength of the affinity which this substance has for oxygen. Naphtha, that has been exposed to the air, soon oxydises the basis of potash, and a brown soap collects round the globule. The concrete oils, tallow, spermaceti, and wax, when heated, likewise combine with it, and form saponaceous compounds; coaly matter is deposited, and carburetted hydrogen gas is evolved. The gas first emitted is hydrogen, arising from the decomposition of the water absorbed by the metallic globule, in its passage through the air. The volatile oils are likewise decomposed by the base of potash with rapidity, when assisted by heat; potash is generated, charcoal precipitated, and some gaseous fluid is disengaged, Camphor, previously fused, is rendered black by its action, a soap is formed, but no gas becomes liberated; and this seems to shew that camphor contains more oxygen than volatile oils.

The metallic oxyds, when heated with the basis of potash, readily become metallic. When a small quantity of oxyd of iron is heated with the base of potash, at a temperature

approaching to its point of distillation, a vivid action take place, the alkali re-appears, and grey metallic particles are obtained, which are soluble with effervescence in muriatic acid. The oxyds of tin and of lead are reduced with more facility, and, if the basis of potash is in excess, an alloy is obtained with the reduced nietal,, Flint glass and green glass are speedily decomposed by it when assisted by a gentle heat. At a temperature of ignition it alters even the purest glass; the oxygen in the alkali of the glass appears to be divided between the two bases, one part being taken up by the basis of potash, and the other remaining with the alkali of the glass; so that by repeatedly distilling and heating this substance in glass tubes, a brown crust, which slowly decomposes water or oxyds in the first state of oxygenation, not only lines the interior of the tube, but even penetrates in many parts through its substance. Mr. Davy also persuades himself that it is more than probable that the silex of the glass likewise suffers some change, and perhaps decomposition. This however is certainly a mere conjecture. Such are the leading characters of the basis of potash.

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The subject of the fifth section is the Properties and Nature of the Basis of Soda. The basis of this alkali is a white metal, of a metallic lustre, greatly resembling silver. It is much softer than other metals, and exceedingly malleable; globules of it may be easily made to weld into one mass by a strong pressure at common temperatures. A globule of th orth of an inch in diameter niay be made to cover a surface of a quarter of an inch, even when its temperature is lowered to 320. It conducts electricity and heat, like the basis of potash, and minute globules of it take fire by the voltaic spark, and burn with bright explosions. Its specific gravity, as Mr. D. inferred from placing it in a mixture of naphtha and oil of sassafras, in which it remains at rest above and below, is equal to ,9348. It requires a higher temperature to effect fusion, than the basis of potash. It melts at 180°, so that it readily fuses under boiling naphtha. It remains fixed in a state of ignition at the melting point of plate glass. On exposure to air, it tarnishes, and readily becomes covered with a white crust, which gradually attracts moisture and forms liquid soda. Heat assists its combination with oxygen, but no luminous appearance takes place till the temperature increases nearly to ignition. When made to burn in oxygen gas, it sends forth bright sparks, and glows like charcoal, but much brighter. On hydrogen gas it has no action. In oxymuriatic acid gas it takes fire and burns vividly with numerous scintillations of bright red colour, and muriate of soda is formed. When thrown upon

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cold water it occasions a hissing noise; hydrogen gas is disengaged, and the oxygen of the water converts it into soda. In this operation there is no luminous appearance. When presented to hot water, the action is more violent; some minute particles of the base are thrown out of the water sufficiently heated to burn in their passage through the atmosphere. When a globule of the base is made to act on a very minute portion of water, the heat evolved is usually sufficient to inflame the base. It acts on alcohol and ether like the basis of potash. When nitrous acid is brought into contact with it, a rapid inflammation takes place; with muriatic acid and sulphuric acid there is a rapid disengagement of heat, but no luminous appearance. Immersed under the surface of acids, it is rapidly oxygenised; soda is produced, and the other products are similar to those generated by the action of the basis of potash. The same is the case when fixed and volatile oils or naphtha are made to act on it When it is fused with dry soda, a division of oxygen takes place between the alkali and the base, and a deep brown fluid is obtained which becomes a dark solid on cooling. This mass, on exposure to air, becomes moist and furnishes soda. A similar substance is often obtained during the decomposition of soda by galvanic electricity, and it may also be generated where the basis of soda is fused in tubes made of plate glass. It unites to sulphur with great eagerness in vessels filled with the vapours of naphtha; light is emitted, and a deep grey sulphuret is produced; this experiment is often attended with an explosion. It also combines under the same circumstances with phosphorus; the phosphuret has the appearance of lead, and becomes changed on exposure to air, or by combustion, into phosphate of soda. The basis of soda in the quantity of

renders mercury solid, of the colour of silver; the combi nation is attended with much heat. It also alloys with tin, lead, and gold; these alloys become readily converted into soda by exposure to air, or by the contact of water, which is decomposed with the evolution of hydrogen. The amalgam of mercury with the basis of soda seems to form triple compounds with other metals: iron and platina appearing to remain in union with the mercury after the separation of sodą by the process of oxydisement. The amalgam of the basis of soda and mercury likewise combines with sulphur, and forms a triple compound of a dark grey colour.

Section VI exhibits the proportions of the peculiar bases and oxygen, in potash and soda.

To ascertain the quantity of oxygen absorbed by the bases of the alkalies, oxygen gas was made to pass through a tube containing the base, and then applying heat to burn them.

In conducting these experiments many difficulties occurred. When the flame of the lamp was immediately brought to play upon the glass the combustion was very vivid, so as sometimes to break the tube; and the alkali generated partly rose in white fumes, which were deposited upon the glass.

When the temperature was slowly raised, the bases acted upon the [silver] tray and formed alloys, and in this state it was very difficult to combine them with their full proportion of oxygene; and glass alone could not be employed on account of its decomposition by the alkaline bases; and porcelain is so bad a conductor of heat, that it was not pos sible to raise it to the point required for the process, without softening the glass.

After the combustion, the absorption of gas was ascertained. In some cases the purity of the residual air was ascertained, in others the alkali formed in the tray was weighed.' pp. 26, 27.

In the first of two experiments on the synthesis of potash by combustion, described by Mr. D., the quantity of basis of potash employed was ,12 grains; the combustion was made on platina, and the basis appeared to be perfectly saturated. The oxygen gas absorbed was equal in bulk to 190 grains of quicksilver. The pressure of the barometer during the experiment was 29, 6; the temperature 62°. In the second experiment, ,07 grains of the basis absorbed a quantity of oxygen equal in bulk to 121 grains of mercury barometer 30, 1; thermometer, 630. If we take the mean of these experiinents, 100 parts of potash will contain 86,1 of the bases and 13,9 of oxygen. In the most accurate experiment which Mr. Davy made on the composition of the basis of soda, 08 parts of the basis absorbed oxygen equal in bulk to 206 grains of quicksilver at 29, 4 barometer, and 56° thermometer; hence at the mean pressure soda contains 80 of the base, and 20 of


The composition of the fixed alkalies was farther investigated, by ascertaining the quantity of hydrogen evolved during the decomposition of water, by the action of the metallic bases of the alkalies, and their subsequent reproduction. An amalgam of ,08 grains of the basis of potash with three grains of quicksilver, acting in water, evolved a quantity of hydrogen gas equal in bulk to 293 grains of mercury; therm. 56; bar. 29.6. This volume of hydrogen gas would require for its combustion a quantity of oxygen equal in voJume to 154, 9 of Mercury; and hence 100 parts of potash appear to be composed of about 84 base and 16 oxygen. In an experiment made on the decomposition of water by the basis of soda, at 30.4 bar. and 52° therm. the volume of hydrogen gas evolved by the action of,054 grains of basis equalled that of 326 grains of quicksilver: hence soda contains 76 base, and 24 oxygen, From these experiments, we are authorised

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