Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 163

=Pota.s.sium, Acetate of.= KC_{2}H_{3}O_{2}. _Syn._ ACETATE OF POTASH, POTa.s.sIC ACETATE; POTa.s.sae ACETAS (B. P., Ph. L., E., D.). _Prep._ (Ph. L.) Acetic acid, 26 fl. oz.; distilled water, 12 fl. oz.; mix, and add, gradually, carbonate of pota.s.sium, 1 lb., or q. s. to saturate the acid; next, filter the solution, and evaporate it by the heat of a sand bath, gradually applied, until the salt is dried.

_Prop., &c._ Acetate of pota.s.sium, prepared as above, occurs in shining white ma.s.ses, having a foliated soft texture, a slight but peculiar odour, and a warm sharp taste; it deliquesces in the air; dissolves in rather less than its own weight of water, and in about twice its weight of alcohol; and by exposure to a red heat is converted into pure carbonate of pota.s.sium. In trade it is preserved in well-corked and sealed bottles.

_Pur._ It is entirely soluble in water, and in rectified spirit. These solutions neither affect litmus nor turmeric, nor are they disturbed by either chloride of barium or nitrate of silver; but if from a stronger solution anything is thrown down by nitrate of silver, the same is again dissolved on the addition of water or dilute nitric acid. Sulphuric acid being added, the vapour of acetic acid is evolved. 100 gr. of this salt, digested in sulphuric acid, the solution evaporated, and the residuum dried at a high temperature, furnish 888 gr. of sulphate of pota.s.sium.

_Uses, &c._ Acetate of pota.s.sium has been found useful in dropsies, febrile affections, jaundice, scurvy, calculus, and several chronic skin diseases. During its exhibition the urine becomes at first neutral, and then alkaline, owing to the salt being converted into carbonate of pota.s.sium in the system.--_Dose._ As a diaph.o.r.etic and antis...o...b..tic, 15 to 20 gr.; as a diuretic, 20 to 60 gr.; as an aperient, 2 to 3 dr.; in each case dissolved in some bland liquid, or in the infusion of some mild vegetable bitter.

=Pota.s.sium Antimoniates.= The normal pota.s.sic antimoniate may be obtained by heating, in an earthen crucible, 1 part of metallic antimony with 4 parts of nitrate of potash. The ma.s.s so obtained is reduced to powder, and afterwards washed with warm water to remove the excess of potash and pota.s.sic nitrite. The residue must be boiled in water for an hour or two; the insoluble anhydrous antimoniate is thus converted into a soluble hydrated modification (K_{2}Sb_{2}O_{6},5H_{2}O.) The insoluble residue now consists chiefly of acid antimoniate of pota.s.sium. The normal salts possess the property of readily dissolving the acid antimoniate, which is precipitated when such a solution is mixed with any neutral salt of one of the alkalies. The normal antimoniate does not crystallise, and has an alkaline reaction.

Acid antimoniate of pota.s.sium (K_{2}Sb_{4}O_{11}.) may be procured by pa.s.sing a stream of carbonic anhydride through a solution of the normal antimoniate.

Acid metantimoniate of potash, or hydro-pota.s.sic metantimoniate is prepared as follows:--Pota.s.sic antimoniate is first formed by deflagrating antimony with nitre, the residue being washed and boiled as described above, so as to bring the whole of the normal antimoniate into solution; the resulting liquid is filtered, and evaporated to a syrup consistence in a silver dish, fragments of caustic potash are then added, and the evaporation is continued until a drop of liquid placed upon a cold slip of gla.s.s begins to crystallise; it is then allowed to cool and the alkaline supernatant liquid is poured off the crystals, which are allowed to drain upon a porous tile. This salt is employed as a test for sodium.

=Pota.s.sium, a.r.s.eniate of.= KH_{2}AsO_{4}. _Syn._ a.r.s.eNIATE OF POTa.s.sA, MONOPOTa.s.sIC a.r.s.eNIATE, POTa.s.sIUM DIHYDRIC a.r.s.eNIATE; POTa.s.sae BINa.r.s.eNIAS, L. _Prep._ Take of a.r.s.enious acid (white a.r.s.enic) and nitrate of pota.s.sium, of each, in powder, 1 part; heat the mixture to dull redness in a gla.s.s flask, until it fuses and red vapours cease to be evolved; dissolve the residuum, when cold, in boiling distilled water, 50 parts; concentrate the solution by evaporation, and set it aside to crystallise.

_Prop., &c._ This salt forms large crystals, which are permanent in dry air, soluble in about 4-1/2 parts of water, and insoluble in alcohol. It is reputed tonic, alterative, and antiperiodic.--_Dose_, 1/16 to 1/8 gr.

dissolved in sweetened water. It is also used to form a resist-paste in calico printing, and in the manufacture of cobalt blue.

=Pota.s.sium, Borate of.= K_{4}B_{4}O_{8}. _Syn._ POTa.s.sae BORAS, L. _Prep._ From dry carbonate of pota.s.sium and dry boracic acids, equal parts, reduced to powder, and heated to redness in a covered crucible; the sublimed ma.s.s, when cold, being dissolved in boiling water, and the filtered solution concentrated by evaporation, and then set aside to crystallise; or at once completely evaporated to dryness.--_Dose_, 1 to 6 gr.; in calculi, &c.

=Pota.s.sium, Borotartrate of.= _Syn._ POTa.s.sae BOROTARTRAS, CREMOR TARTARI SOLUBILIS, L.; CReME DE TARTRE SOLUBLE, Fr. _Prep._ (P. Cod.) Crystallised boracic acid, 1 part; bitartrate of pota.s.sium, 4 parts; water, 24 parts; dissolve, by the aid of heat, in a silver basin, and, constantly stirring, evaporate the resulting solution, either to dryness, and then powder it, or merely to a syrupy consistence, when it may be spread upon plates, and dried in scales, by the heat of a stove. It must afterwards be preserved from the air.

_Prop., &c._ A white, deliquescent powder, freely soluble in water. It has been used as a solvent for lithic calculi, and in gout, &c.--_Dose_, 15 to 30 gr. In doses of 2 to 3 dr. it is laxative, and is very popular as such on the Continent.

=Pota.s.sium, Bromide of.= KBr. _Syn._ POTa.s.sII BROMIDUM (B. P.). _Prep._ Exactly as the iodide, which it resembles in its character, only being somewhat less soluble in water and more in alcohol. Employed in similar cases and given in similar doses to the iodide.

=Pota.s.sium, Carbonate of.= K_{2}CO_{3}. _Syn._ CARBONATE OF POTa.s.sA, SUBCARBONATE OF POTa.s.sA, SALT OF TARTAR; POTa.s.sae CARBONAS (B. P., Ph. L., E., D.). Impure or crude carbonate of pota.s.sium is chiefly imported from America and Russia, and is obtained by lixiviating wood ashes, and evaporating the solution to dryness. The ma.s.s is then transferred into iron pots, and is kept in a state of fusion for several hours, until it becomes quiescent, when the heat is withdrawn, and the whole is left to cool. It is next broken up and packed in air-tight barrels, and in this state const.i.tutes the 'potashes' or 'potash' of commerce. Another method is to transfer the black salts, or product of the first evaporation, from the kettles to a large oven or furnace, so constructed that the flame is made to play over the alkaline ma.s.s, which is kept constantly stirred by means of an iron rod. The ignition is continued until the impurities are burned out, and the ma.s.s changes from a blackish tint to a dirty or bluish white. The whole is next allowed to cool, and is then broken into fragments, and packed in casks as before. It now const.i.tutes 'pearlash.'

When pearlash is dissolved in cold distilled water, the solution depurated, filtered and crystallised, or simply evaporated to dryness, it forms 'refined ashes,' or carbonate of potash sufficiently pure for most pharmaceutical and technical purposes. The granulated carbonate of potash, salt of tartar, or prepared kali, of the shops, is simply refined ashes which, during the evaporation, and more especially towards the conclusion of the desiccation, has been a.s.siduously stirred, so that it may form small white granulations, instead of adhering together to form an amorphous solid ma.s.s. In this state it const.i.tutes the ordinary or carbonate of pota.s.sa of the Pharmacopias. Ordinary potash or pearlash may be refined as follows:--Raw potash, 10 parts, is dissolved in cold water, 6 parts, and the solution is allowed to remain for 24 hours, in a cool place; it is then filtered, and somewhat concentrated by evaporation, crystallisation being prevented by continually stirring the ma.s.s until the whole is nearly cold; it is next decanted into a strainer, and the mother-liquor allowed to drip off; the residuum is evaporated to dryness at a gentle heat, and redissolved in an equal quant.i.ty of cold distilled water; the new solution, after filtration, is again evaporated to dryness.

The product is quite free from pota.s.sium sulphate, and is nearly free from both pota.s.sium chloride and silicates.

=Pota.s.sium, Pure Carbonate of.= CARBONATE OF POTa.s.sA (POTa.s.sae CARBONAS PURUM--Ph. E. & D., and Ph. L., 1836).--(Ph. L., 1836.) From bicarbonate of pota.s.sium, in crystals, heated to redness in a crucible.

(Ph. E.) As the last. Or, more cheaply, by dissolving bitartrate of pota.s.sium in thirty parts of boiling water, separating and washing the crystals which form on cooling, heating them in a loosely covered crucible to redness as long as fumes are discharged, breaking down the ma.s.s, and roasting it in an oven for two hours, with occasional stirring; lixiviating the product with (cold) distilled water, filtering the solution thus obtained, evaporating it to dryness, granulating the salt towards the close by brisk agitation; and, lastly, heating the granular salt thus obtained nearly to redness.

(Ph. D.) Bitartrate of pota.s.sium, 2 lbs., is exposed to a red heat in an iron crucible, as before; the powdered calcined ma.s.s is boiled for 20 minutes in water, 1 quart, the solution filtered, and the filtrate washed with water, 1 pint, to which ammonium sesquicarbonate, 1/2 oz., has been added; the mixed and filtered liquors are evaporated to dryness, and, a low red heat having been applied, the residuum is rapidly reduced to powder in a warm mortar, and at once enclosed in (dry and) well-stoppered bottles.

_Prop._ These are well known. It exhibits most of the properties of hydrate of pota.s.sium, but in a vastly less degree. It is very deliquescent, effervesces with acids, exhibits a marked alkaline reaction with test paper, is insoluble in alcohol, but dissolves in less than its own weight of water, its affinity for the last being so great that it takes it from alcoholic mixtures.

_Pur., &c._ Carbonate of pota.s.sium frequently contains an undue quant.i.ty of water, as well as silicic acid, sulphates, and chlorides. The water may be detected by the loss of weight the salt suffers when heated; the silica, by adding to it hydrochloric acid in excess, evaporating to dryness, and igniting the residuum, by which this contamination is rendered insoluble; the sulphates and chlorides may be detected by adding nitric acid in excess, and testing the liquid with nitrate of silver and chloride of barium. If the former produces a white precipitate, a chloride is present; and if the latter does the same, the contamination is a sulphate. Carbonate of pota.s.sium deliquesces in the air, and is almost entirely dissolved by water; in an open vessel it spontaneously liquefies.

It changes the colour of turmeric brown. Supersaturated with nitric acid, neither carbonate of sodium nor chloride of barium throws down anything, and nitrate of silver very little. 100 gr. lose 16 gr. of water by a strong red heat; and the same weight loses 263 gr. of carbonate anhydride when placed in contact with dilute sulphuric acid.

=Pota.s.sium, Bicarbonate of.= KHCO_{3}. _Syn._ POTa.s.sIUM HYDROGEN CARBONATE, BICARBONATE OF POTa.s.sA; POTa.s.sae BICARBONAS (B. P., Ph. L., E., & D.). _Prep._ 1. (Ph. L. 1836.) Carbonate of pota.s.sium, 6 lbs.; distilled water, 1 gall.; dissolve, and pa.s.s carbonic anhydride (from chalk and sulphuric acid diluted with water) through the solution to saturation; apply a gentle heat, so that whatever crystals have been formed may be dissolved, and set aside the solution that crystals may again form; lastly, the liquid being poured off, dry them.

2. (Ph. D.) Carbonic anhydride, obtained by the action of dilute hydrochloric acid on chalk (the latter contained in a perforated bottle immersed in a vessel containing the acid), is pa.s.sed, by means of gla.s.s tubes connected by vulcanised india rubber, to the bottom of a bottle containing a solution of carbonate of pota.s.sium, 1 part, in water, 2-1/2 parts; as soon as the air is expelled from the apparatus the corks through which the tubes pa.s.s are rendered air-tight, and the process left to itself for a week; the crystals thus obtained are then shaken with twice their bulk of cold water, drained, and dried on bibulous paper, by simple exposure to the air. From the mother-liquor, filtered, and concentrated to one half, at a heat not exceeding 110 Fahr., more crystals may be obtained. The tube immersed in the solution of carbonate of pota.s.sium will have to be occasionally cleared of the crystals with which it is liable to become choked, else the process will be suspended.

3. (Ph. B.) The same.

4. (Apothecaries' Hall, London.) Pota.s.sium carbonate, 100 lbs.; distilled water, 17 galls.; dissolve, and saturate the solution with carbonic anhydride, as in No. 1, when 35 to 40 lbs. of crystals of bicarbonate of pota.s.sium may be obtained; next dissolve carbonate of pota.s.sium, 50 lbs., in the mother-liquor, and add enough water to make the whole a second time equal to 17 galls.; the remaining part of the operation is then to be performed as before. This plan may be repeated again and again, for some time, provided the carbonate used is sufficiently pure.

5. (Ph. E.) Take of carbonate of pota.s.sium, 6 oz.; sesquicarbonate of ammonium, 3-1/2 oz.; triturate them together, and, when reduced to a very fine powder and perfectly mixed, make them into a stiff paste with a very little water; dry this, very carefully, at a heat not higher than 140 Fahr., until a fine powder, perfectly devoid of ammoniacal odour, be obtained, occasionally triturating the ma.s.s towards the end of the process.

6. (Commercial.) From carbonate of pota.s.sium, in powder, made into a paste with water, and exposed for some time on shallow trays, in a chamber filled with an atmosphere of carbonic anhydride, generated by the combustion of either c.o.ke or charcoal, and purified by being forced through a cistern of cold water; the resulting salt is next dissolved in the least possible quant.i.ty of water at the temperature of 120 Fahr., and the solution filtered and crystallised.

_Prop._ It is soluble in 4 times its weight of water at 60 Fahr.; is fixed in the air, but loses carbonic acid below the temperature of a carbonate at a red heat. It possesses the general alkaline properties of carbonate of pota.s.sium, but in an inferior degree, having only a slightly alkaline taste, and, when absolutely pure, not affecting the colour of turmeric.

_Pur._ In a solution of pure bicarbonate of pota.s.sium a solution of mercuric chloride merely causes an opalescence, or very slight white precipitate; if it contains carbonate, a brick-coloured precipitate is thrown down. From 100 gr. of the pure crystals of bicarbonate, 307 gr. of water and carbonic acid are expelled at a red heat. In other respects it may be tested like the carbonate.

_Uses, &c._ Bicarbonate of pota.s.sium is the most agreeable of all the salts of pota.s.sium, and is much used as an antacid or absorbent, and for making effervescing saline draughts. It has also been successfully employed in rheumatism, scurvy, gout, dyspepsia, and various other diseases in which the use of pota.s.sium is indicated. The dose is from 10 gr. to 1/2 dr.

20 gr. bicarbonate, in crystals, ---------------------/---------------------

are equivalent to

---------------------/--------------------- 14 gr. of crystallised nitric acid, 15 gr. of crystallised tartaric acid, and 1/2 oz. of lemon juice.

=Pota.s.sium, Chlorate of.= KClO_{3}. _Syn._ CHLORATE OF POTASH; POTa.s.sae CHLORAS (B. P., Ph. L. & D.), L. _Prep._ 1. Chlorine gas is conducted by a wide tube into a moderately strong and warm solution of hydrate or carbonate of pota.s.sium, until the absorption of the gas ceases and the alkali is completely neutralised; the liquid is then kept at the boiling temperature for a few minutes, after which it is gently evaporated (if necessary) until a pellicle forms on the surface, and is next set aside, so as to cool very slowly; the crystals, thus obtained, are drained and carefully washed on a filter, with ice-cold water, and are purified by re-solution and re-crystallisation. The product is chlorate of pota.s.sium.

The mother-liquor, which contains much chloride of pota.s.sium mixed with some chlorate, is either evaporated for more crystals (which are, however, less pure than the first crop) or is preserved for a future operation.

_Obs._ The product of the above process is small, varying from 10 to 45% of the weight of the pota.s.sium consumed in it, according to the skill with which it is conducted; this apparent loss of pota.s.sium arises from a large portion of it being converted into chloride, a salt of comparatively little value. The following processes have been devised princ.i.p.ally with the view of preventing this waste, or of employing a cheaper salt of pota.s.sium than the carbonate:--

2. (Ph. B.) Mix slaked lime, 53 oz., with carbonate of potash, 20 oz., and triturate them with a few ounces of distilled water, so as to make the mixture slightly moist. Place oxide of manganese, 80 oz., in a large retort or flask, and having poured upon it hydrochloric acid, 24 pints, diluted with 6 pints of water, apply a gentle sand heat, and conduct the chlorine as it comes over, first through a bottle containing 6 oz. of water, and then into a large carboy containing the mixture of carbonate of potash and slaked lime. When the whole of the chlorine has come over remove the contents of the carboy and boil them for 20 minutes with 7 pints of distilled water; filter and evaporate till a film forms on the surface, and set aside to cool and crystallise.

The crystals thus obtained are to be purified by dissolving them in 3 times their weight of boiling distilled water, and again allowing the solution to crystallise.--_Dose_, 10 gr. to 30 gr.

3. A solution of chloride of lime is precipitated with a solution of carbonate of pota.s.sium, and the liquid, after filtration, saturated with chlorine gas; it is then evaporated and crystallised as before. Dr Ure has suggested the subst.i.tution of sulphate of pota.s.sium for the carbonate, by which the process would be rendered very inexpensive.

4. Carbonate of pota.s.sium, 69 parts of the dry or 82 parts of the granulated, hydrate of calcium, 37 parts (dry fresh slaked lime), both in powder, are mixed together, and exposed to the action of chlorine gas, to saturation (the gas is absorbed with great rapidity, the temperature rises above 212 Fahr., and water is freely evolved); the heat, with free exposure, is then maintained at 212 for a few minutes (to remove some trace of 'hypochlorite'), the residuum, consisting of chlorate of pota.s.sium and chloride of calcium, is treated with hot water, and the chlorate of pota.s.sium crystallised out of the resulting solution, as before. This process, which is an excellent one (the loss of pota.s.sium being for the most part avoided), has been modified and improved by various authorities, as will be seen below.

5. A solution of chloride of lime (18 to 20 Baume) is heated in a leaden or cast-iron vessel, and sufficient of a salt of pota.s.sium added to raise the density of the liquid 3 or 4 hydrometer degrees; the solution is then quickly, but carefully, concentrated until the gravity rises to 30 or 31 Baume, when it is set aside to crystallise. A good and economical process.

6. Chloride of pota.s.sium, 76 parts, and fresh calcium hydrate, 222 parts, are reduced to a thin paste with water, q. s., and a stream of chlorine gas pa.s.sed through the mixture, to saturation; chloride of calcium and chlorate of pota.s.sium are formed; the last is then removed by solution in boiling water, and is crystallised as before. This process, which has received the approval and recommendation of Liebig, has long been practised in Germany, and was originally introduced to this country by Dr Wagenmann. The product is very large, and of excellent quality.

_Prop._ White, inodorous, four-or six-sided pearly scales, soluble in about 20 parts of cold and 2-1/2 parts of boiling water; in taste it resembles nitre, but is somewhat more austere; at about 450 Fahr. it undergoes the igneous fusion, and on increasing the heat almost to redness effervescence ensues, and fully 39% of pure oxygen gas is given off, whilst the salt becomes changed into chloride of pota.s.sium. When mixed with inflammable substances and triturated, heated, or subjected to a smart blow or strong pressure, or moistened with a strong acid, it explodes with great violence.

_Pur., Tests, &c._ The usual impurity of this salt is chloride of pota.s.sium, arising from careless or imperfect manipulation. When this is present, a solution of nitrate of silver gives a curdy white precipitate, soluble in ammonia; whereas a solution of the pure chlorate remains clear.

_Uses._ Chlorate of pota.s.sium is princ.i.p.ally used in the manufacture of lucifer matches, fireworks, oxygen gas, &c., and as an oxidising agent in calico printing. It was formerly used to fill percussion caps, but was abandoned for fulminating mercury, on account of its disposition to rust the nipples of the guns. As a medicine it is stimulant and diuretic. It has been given in dropsy, syphilis, scurvy, cholera, typhus, and other depressing affections. It gives a fine artificial colour to the blood.

(Stevens.)--_Dose_, 5 to 15 gr., in solution, twice or thrice a day.

_Concluding Remarks._--Formerly, chlorate of pota.s.sium was a salt which was made only on the small scale, and chiefly used in experimental chemistry; now it is in considerable demand, and forms an important article of chemical manufacture. The latter has hence, of late years, received considerable attention and improvement in the leading laboratories of Europe. The chlorate requires to be handled with great care. It should never be kept in admixture with any inflammable substance, more especially with sulphur, phosphorus, or the sulphides, as these compounds are exploded by the most trivial causes, and, not unfrequently, explode spontaneously.

=Pota.s.sium, Chloride of.= KCl. _Syn._ CHLORIDE OF POTa.s.sA. _Prep._ The chloride of pota.s.sium of commerce is usually a secondary product in the manufacture of chlorate of pota.s.sium and other substances. The mother-liquor of the former is evaporated to dryness and heated to dull redness, the calcined ma.s.s is then dissolved in water, the solution purified by defecation and evaporated down for crystals.

It can also be well prepared by neutralising boiling solution of carbonate of pota.s.sium by dilute hydrochloric acid, evaporating down, and crystallising.

_Prop., &c._ It closely resembles culinary salt in appearance; is anhydrous; dissolves in about 4 parts of cold and 2 of boiling water; has a slightly bitter, saline taste; fuses at a red heat; and is volatilised at a very high temperature. As a medicine it is diuretic and aperient. It was formerly in high repute as a resolvent and antis...o...b..tic, and, particularly, as a remedy for intermittents. It is now seldom used.--_Dose_, 10 gr. to 1/2 dr., or more.