A L K

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A L K

from water of composition, anti knowing tirequantity of alkali produced by the alkalinebasis, it was easy to compare the saturatingpowers of these alkalies with those of the fusedpotash and soda prepared by alcohol. Fromthese data 100 parts of fused potash preparedby alcohol contain 20.72 of water of compo-sition : and 100 parts of fused soda contain23.80 of water.

The authors take as a mean from these ex-periments (rejecting the first as far as regardsthe potash as being imperfect; that causticpotash, prepared in the common way by alco-hol, and fused at a red heat, contains a fifthof its weight of water-, and fused soda afourth.

We may observe however that these resultsdiffer much too widely to be a fair subjectfor taking an average, except in a very generalway. Perhaps, too, it is impossible to fixprecisely the quantity of water contained inthe fused caustic alkali, as this may vary ac-cording to the heat employed and other cir-cumstances. It shews however that this formof alkali is certainly a Ilydrnt, or one thatcontains a notable quantity of water of com-position, and also that no great dependance isto be placed on the accuracy of any calculationon the proportions of the alkaline neutral salts,which is founded on the quantities of theHydrated Alkali employed.

ALKALINE BASIS. Potassium. Sodium.

One of the most interesting discoveries ofmodern chemistry is the decomposition of thefixed alkalies which had often been conjecturedto be of a compound nature, but no evidence ofthe truth of this opinion had ever been giventill Sir H. Davy applied to this enquiry theas'tonishing powers of electro-chemical agency.The researches which he had made on the de-composition of acids and neutral salts by gal-vanic electricity were full of new and most in-teresting results, they pointed out a mode ofchemical analysis far more powerful than anythat had been hitherto undertaken, and the ad-mirable skill in contriving experiments, andsagacity in deducing from them the general lawsof chemical decomposition, enabled him tomake the brilliant discovery which is the sub-ject of this article. He conjectured that if afreed alkali was an oxyd of some unknownbase, it was probable that when it was subjectedto the.action of opposite electricities, the oxy-gen of the alkali would be conveyed to the

* Phil. Tra

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positive pole, whilst the inflammable base wouldappear in a separate state at the negative pole.

Some difficulties au-se at first in selecting aproper mode of conducting the experiment.When a solution of the alkali was used, theelectric power was expended chiefly in the de-composition of the water present; and on theother hand, when the alkali was dry and fusedat the time of applying the electric power, itwas indeed decomposed, but the basis instantlyburnt with a most intense light and flame, andcould not be collected. The great difficulty inthe experiment was that the alkali, when driedand fused, is a non-conductor of electricity ;but it was found that slightly moistening thesurface renders it a conductor, and in this stateit readily fuses and is decomposed by strongelectrical powers.

The basis of potash vyas thus discovered. 1A small piece of potash which had been ex-posed for a few seconds to the atmosphere, so asto give conducting powers to the surface, wasplaced upon an insulated disk of platina, con-nected with the negative side of the galvanicbattery in intense activity, and a platina wirecommunicating with the positive side wasbrought into contact with the upper surface ofthe alkali. A vivid action soon took place. Thepotash began to fuse at both points of con-tact ; there was a violent effervescence at thepositive surface, and at the negative therewas no liberation of elastic fluid, but small glo-bules having a high metallic lustre, exactlyresembling quicksilver in appearance, wereformed, some of which immediately after burntwith explosion and bright flame, while othersremained being first tarnished, and finallycovered by a white film on tlieir surfaces. Thegas liberated at the positive surface was foundto be pure oxygen, and the globules were foundby numerous experiments to be a peculiar in-flammable principle, the Basis of Potash . Theplatina was in no way connected with the resultexcept as a medium for the electric power, forthe same effects were produced by substitutingcopper, gold, plumbago or charcoal.

Soda when acted on in the same mannergave a similar result, but it required a greaterintensity of galvanic action to produce theBaris of Soria With a good battery of 1006-inch plates, the Basis of Potash could be ob-tained from pieces of the alkali weighing 40 or50 grains, which made the distance betweenthe opposite wires nearly a of an inch ; hutwith the same galvanic power, pieces of sodai- for 1 S 08 .