PART III.

Alkalies astd Neutral Salts.

595

with the lime, and cover the vessel. Pour the materials, as soonas they are cold, into a glass funnel, the tube of which is ob-structed with a linen rag. Cover the funnel, and allow thelixivium to drop into a vessel placed below it, peering waterinto the funnel occasionally, until three pounds are filtered.Let the solution be shaken, and preserved in a well-stopt greenglass bottle.

"If the ley be rightly prepared it will be colourless, ino-dorous, and will scarcely effervesce when mixed with an acid.If it effervesce considerably, let a small portion of fresh burntlime, in fine powder, be added; digest for twenty-four hoursin a covered vessel, frequently agitating; and finally, filter theley in the manner already directed,

" The specific gravity of this solution is, to that of distilledwater, as 1100 to 1000."

Si/n. Dissolution de Potasse (F.), Fliissiges atzendes Kali (G.)> Liquore diPotassa(/.).

In considering the proportions of the two latter of these pro-cesses, there appears, a priori, a much larger proportion of limeordered than is necessary for the decomposition of the subcar-bonate of potass; but if the theory of Berthollet', as to theeffect of quantity in influencing chemical affinities, be just,this superabundance is necessary to insure the more perfectseparation of the carbonic acid from the potass. If the lime,however, be well burnt, and recent, the solution is obtained al-most perfectly free from carbonic acid, by the quantity orderedin the London formula; but unless much care be taken to ex-clude the air during the filtration, it will be rapidly attractedfrom the atmosphere. Calico is the best substance for stoppingthe mouth of the funnel, and it should be supported on a roughpebble or siliceous stone, previously dropped into the funnel,and allowed to settle itself. It should be kept in small glassbottles, fitted with ground stoppers.

Qualities. — Solution of potass is inodorous, and so causticas not to admit of being tasted. It is limpid, colourless, dense,and has an oily appearance when agitated ; does not effervescewith acids, nor afford a precipitate with lime-water; and feelssoapy when rubbed between the fingers, owing to the solutionof the cuticle. When perfectly pure, it remains transparenton the addition of barytic water. Prepared according to theformulae of the pharmacopoeias, it is not a simple solution ofpotass, but contains small portions of muriate, and sulphate ofpotass, silica, and generally some lime. The presence of mu-riates may be discovered by saturating a portion of the solutionwith nitric acid, then adding nitrate of barytes to precipitatethe sulphates, if any; and lastly, adding a solution of nitrateof silver, which is precipitated if any muriate be present.

1 Chemical Statics, vol. i.2«2