Chapter XLVIII: Part 2 (9)

=Pommade of Cucumbers.= _Syn._ POMMADE DE CONCOMBRES, UNGUENTUM CUCUMIS. _Prep._ Lard, 10 oz.; veal suet, 6 oz.; balsam of tolu, 9 gr.; rose water, 44 minims; cucumber juice, 12 oz., by weight. Melt the lard and the suet over a water bath, and add the tolu, previously dissolved in a little alcohol, and then the rose water. When clear, decant it into a tinned basin, then add to a third of the cucumber juice, and stir continually for 4 hours; pour off the juice and add another third, stir as before, then pour off, and add the remainder of the juice; separate as much as possible the fat from the liquid, melt by a water bath, and after some hours skim, and put into pots. (Beat, when in a semi-liquid state, with a wooden spatula, when it will become much lighter and nearly double in bulk.)

=Pommade d’Alyon.= See OINTMENT OF NITRIC ACID. See CUPS.

=Pommade de Beauté.= _Prep._ From oil of almonds, 2 oz.; spermaceti, 2 dr.; white wax, 1-1/2 dr.; glycerin, 1 dr.; balsam of Peru, 1/2 dr.; mixed by a gentle heat. Used as a skin cosmetic as well as for the hair.

=Pommade de Casse.= _Prep._ From plain pommade, 1 lb.; palm oil, 1/2 oz.; melt, pour off the clear, and add oil of cassia and huile au jasmin, of each 1 dr.; neroli, 20 drops; oil of verbena or lemon grass, 15 drops; otto of roses, 5 drops; and stir until nearly cold. Very fragrant.

=Pommade d’Hebe.= _Prep._ To white wax, 1 oz., melted by a gentle heat, add, of the juice of lily bulbs and Narbonne honey, each 2 oz.; rose water, 2 dr.; otto of roses, 2 drops. Applied night and morning to remove wrinkles.

=Pommade de Ninon de l′Enclos.= _Prep._ Take of oil of almonds, 4 oz.; prepared lard, 3 oz.; juice of houseleek, 3 fl. oz. Used chiefly as a skin cosmetic. Said to be very softening and refreshing.

=Pommade Divine.= _Prep._ 1. Washed and purified beef marrow, 2 lbs.; liquid styrax, cypress wood, and powdered orris root, of each 2 oz.; powdered cinnamon, 1 oz.; cloves and nutmegs, of each (bruised) 1/2 oz.; digest the whole together by the heat of a water bath for six hours, and then strain through flannel.

2. Plain pommade, 2 lbs.; essence of lemon and bergamot, of each 2 dr.; oils of lavender and origanum, of each 1 dr.; oils of verbena, cassia, cloves, and neroli, of each 12 drops; huile au jasmin, 3 dr.; essence of violets, 1/2 oz.

=Pommade, Dupuytren’s.= _Prep._ 1. Take of prepared beef marrow, 12 oz.; melt, add of baume nerval (see OINTMENT, NERVINE), 4 oz.; Peruvian balsam and oil of almonds, of each 3 oz.; and lastly, of alcoholic extract of cantharides, 36 gr.; (dissolve in) rectified spirit, 3 fl. dr. This is the original formula for this celebrated pommade. The following modifications of it are now commonly employed:——

2. (Cap.) Beef marrow, 2 oz.; alcoholic extract of cantharides, 8 gr.; rose oil, 1 dr.; essence of lemons, 30 drops.

3. (Guibourt.) Beef marrow and ‘baume nerval’ (page 1179), of each 1 oz.; rose oil, 1 dr.; alcoholic (or acetic) extract of cantharides, 6 gr.; (dissolved in) rectified spirit, q. s. These compounds are used to promote the growth of the hair and to prevent baldness, for which purpose they are usually coloured and scented according to the taste of the manufacturer. To be useful, they should be well rubbed on the scalp, at least once daily, for several weeks, and the head should be occasionally washed with soap-and-water.

=Pommade, East India.= _Prep._ Take of suet, 3 lbs.; lard, 2 lbs.; beeswax (bright), 1/2 lb.; palm oil, 2 oz.; powdered gum benzoin, 3 oz.; musk (previously triturated with a little lump sugar), 20 gr.; digest the whole together in a covered vessel, by the heat of a water bath, for 2 hours, then decant the clear portion, and add, of essence of lemon, 1/2 oz.; oil of lavender, 1/4 oz.; oils of cloves, cassia, and verbena, of each 1/2 dr. A favourite pommade in the East Indies.

=Pommade for Freckles.= (‘New York Druggists’ Circular.’) _Prep._ Citrine ointment and oil of almonds, of each 1 dr.; spermaceti ointment, 6 dr.; oil of roses, 3 drops. Mix well in a wedgwood mortar, using a wooden or bone knife.

=Pommade, Hard.= _Syn._ HARD POMATUM, ROLL P. _Prep._ 1. Take of beef suet, 2 lbs.; yellow wax, 1/4 lb.; spermaceti, 1 oz.; powdered benzoin, 1/4 oz.; melt them together, then add, of oil of lavender, 2 dr.; essence of ambergris, 1/2 dr. Before it concretes pour it into moulds of paper or tin foil.

2. Mutton suet and lard, of each 1 lb.; white wax, 6 oz.; melt, and add, of essence of lemon, 2 dr.; oil of cassia, 1/2 dr. Other perfumes may be employed at will.

Hard pomatums are used to gloss and set the hair. They act both as ‘pommade’ and ‘fixateur.’ See COSMETIQUE.

=Pommade, Macassar.= _Prep._ From castor oil, 5 oz.; white wax, 1 oz.; alkanet root, 1/2 dr.; heat them together until sufficiently coloured, then strain, and add, oil of origanum and oil of rosemary, of each 1 dr.; oil of nutmeg, 1/2 dr.; otto of roses, 10 drops. Said to be equal in efficacy to MACASSAR OIL.

=Pommade, Marechal.= Plain pommade scented by digesting it with _poudre maréchale_.

=Pommade, Marrow.= _Syn._ MARROW POMATUM. _Prep._ From prepared beef marrow, 1/2 lb.; beef suet, 1/4 lb.; palm oil, 1/4 oz.; melted together and scented at will.

=Pommade, Millefleur.= _Prep._ From plain pommade scented with a mixture of essence of lemon and essence of ambergris, each 4 parts; oil of lavender, 2 parts; oil of cloves and essence de petit grain, of each 1 part; or with other like perfumes so proportioned to each other that no one shall predominate. Much esteemed.

=Pommade, Roll.= See POMMADE, HARD.

=Pommade, Roman.= See _below_.

=Pommade, Rose.= _Syn._ ROSE POMATUM. This is plain pommade or hard lard, which has been well beaten with eau de rose, or, better still, scented with otto of roses. It is sometimes tinged with alkanet root.

=Pommade, Soft.= Plain pomatum scented at will.

=Pommade, Soubeiran’s.= _Prep._ From beef marrow, 1-1/2 oz.; oil of almonds, 1/2 oz.; disulphate of quinine, 1 dr. Recommended for strengthening and restoring the hair.

=Pommade, Transparent.= _Prep._ Spermaceti, 2 oz.; castor oil, 5 oz.; alcohol, 5 oz.; oil of bergamot, 1/2 dr.; oil of Portugal, 1/2 dr.

=Pommade, Vanilla.= _Syn._ ROMAN POMMADE, POMMADE À LA VANILLE, POMMADE ROMAIN. From plain pommade and pommade à la rose, of each 12 lbs.; powdered vanilla, 1 lb.; heat them together in a water bath, stir constantly for 1 hour, let it settle for another hour, decant the clear, and add, oil à la rose, 2-1/2 lbs.; bergamot, 4 oz.

=POPPY.= _Syn._ WHITE POPPY; PAPAVER SOMNIFERUM, L. The capsules or fruit (“mature”——Ph. L.; “not quite ripe”——Ph. E.) form the poppies or poppy-heads of the shops (PAPAVERIS CAPSULÆ; PAPAVER——Ph. L., E., & D.). They are anodyne and narcotic, similar to opium, but in only a very slight degree. The seeds (MAW SEED), which are sweet, oleaginous, and nutritious, are used as a substitute for almonds in confectionery and mixtures, and are pressed for their oil. See EXTRACT, OPIUM, and SYRUP.

=Poppy, Red.= _Syn._ CORN POPPY, CORN ROSE; PAPAVER RHŒAS, L. The fresh petals or flowers (RHŒADOS PETALA; RHŒAS——Ph. L., E., & D.) are reputed pectoral, but are chiefly employed on account of their rich colour. See SYRUP.

=POP′ULIN.= _Syn._ POPULINUM, L. A peculiar neutral, crystallisable substance, formerly supposed to be an alkaloid, found, associated with SALICIN, in the root-bark of the _Populus tremula_ (Linn.), or aspen.

_Prep._ Concentrate the decoction by a gentle heat, and set it aside in a cool situation to crystallise; dissolve the crystals which are deposited in rectified spirit, decolour them by digestion with animal charcoal, filter, and again crystallise. To render them still purer they may be redissolved and crystallised a second and a third time, if necessary.

_Prop., &c._ It resembles salicin in appearance and solubility, but, unlike that substance, has a penetrating sweet taste. Dilute acids convert it into benzoic acid, grape sugar, and saliretin; and with a mixture of sulphuric acid and bichromate of potassa it yields a large quantity of salicylous acid. It appears to be tonic, stomachic, and febrifuge.

=POR′CELAIN.= See POTTERY.

=PORK.= The value of pork as an article of diet is well known. That from the young and properly fed animal is savoury, easy of digestion, and, when only occasionally employed, highly wholesome; but it is apt to disagree with some stomachs, and should, in such cases, be avoided. To render it proper for food, it should be thoroughly but not overcooked. When salted it is less digestible. The frequent use of pork is said to favour obesity, and to occasion disorders of the skin, especially in the sedentary. See MEAT.

=POR′PHYRIZED, PORPHORIZA′TION.= Words coined by recent pharmaceutical writers, and possessing similar meanings to LEVIGATED and LEVIGATION.

=PORPHY′ROXIN.= A neutral crystallisable substance discovered by Merck in opium. It is soluble in both alcohol and ether, insoluble in water, and is characterised by assuming a purplish-red colour when heated in dilute hydrochloric acid.

=PORRI′GO.= See RINGWORM.

=POR′TER.= This well-known beverage, now the common drink of the inhabitants of London, by whom it is generally termed ‘beer,’ originated with a brewer named Harwood, in 1722. Previously to this date, ‘ale,’ ‘beer,’ and ‘twopenny,’ constituted the stock in trade of the London publican, and were drunk, either singly or together, under the names of ‘half-and-half’ or ‘three threads,’ for which the vendor was compelled to have recourse to two or three different casks, as the case might demand. The inconvenience and trouble thus incurred led Mr Harwood to endeavour to produce a beer which should possess the flavour of the mixed liquors. In this he succeeded so well that his new beverage rapidly superseded the mixtures then in use, and obtained a general preference among the lower classes of the people. At first this liquor was called ‘entire’ or ‘entire butt,’ on account of it being drawn from one cask only, but it afterwards acquired, at first in derision, the now familiar name of ‘porter,’ in consequence of its general consumption among porters and labourers. The word ‘entire’ is still, however, frequently met with on the signboards of taverns about the metropolis.

The characteristics of pure and wholesome porter are its transparency, lively dark brown colour, and its peculiar bitter and slightly burnt taste. Originally, these qualities were derived from the ‘high-dried malt,’ with which alone it was brewed. It is now generally, if not entirely, made from ‘pale’ or ‘amber malt,’ mixed with a sufficient quantity of ‘patent’ or ‘roasted malt’ to impart the necessary flavour and colour. Formerly, this liquor was ‘vatted’ and ‘stored’ for some time before being sent out to the retailer, but the change in the taste of the public during the last quarter of a century in favour of the mild or new porter has rendered this unnecessary. The best ‘draught porter,’ at the time of its consumption, is now only a few weeks old. In this state only would it be tolerated by the modern beer-drinker. The old and acid beverage that was formerly sold under the name of porter would be rejected at the present day as ‘hard’ and unpleasant, even by the most thirsty votaries of malt liquor.

The ‘beer’ or ‘porter’ of the metropolitan brewers is essentially a weak mild ale, coloured and flavoured with roasted malt. Its richness in sugar and alcohol, on which its stimulating and nutritive properties depend, is hence less than that of an uncoloured mild ale brewed from a like original quantity of malt. For pale malt is assumed to yield 80 to 84 lbs. of saccharine per quarter; whereas the torrefied malt employed by the porter brewers only yields 18 to 24 lbs. per quarter, and much of even this small quantity is altered in its properties, and is incapable of undergoing the vinous fermentation. In the manufacture of porter there is a waste of malt which does not occur in brewing ale; and the consumer must, therefore, either pay a higher price for it or be content with a weaker liquor.

The hygienic properties of porter, for the most part, resemble those of other malt liquors. Some members of the faculty conceive that it is better suited to persons with delicate stomachs and weak digestion than either ale or beer. That there may be some reason for this preference, in such cases, we are not prepared to deny, but undoubtedly, when the intention is to stimulate and nourish the system, ale is preferable. Certain it is, however, that the dark colour and strong taste of porter render its adulteration easier than that of ale, whilst such adulteration is more difficult of detection than in the paler varieties of malt liquors. “For medical purposes, ‘bottled porter’ (CEREVISIA LAGENARIA) is usually preferred to ‘draught porter.’ It is useful as a restorative in the latter stages of fever, and to support the powers of the system after surgical operations, severe accidents, &c.” (Pereira, ii, 982.) When ‘out of condition’ or adulterated, porter, more than perhaps any other malt liquor, is totally unfit for use as a beverage, even for the healthy; and when taken by the invalid, the consequences must necessarily be serious. Dr Ure says that pure porter, “when drank in moderation, is a far wholesomer beverage for the people than the thin acidulous wines of France and Germany.”

The manufacture of porter has been described in our article on BREWING, and is also referred to above. It presents no difficulty or peculiarity beyond the choice of the proper materials. A mixture of ‘brown’ and ‘black malt’ is thought to yield a finer flavour and colour to the pale malt that gives the body to the liquor than when ‘black’ or ‘roasted malt’ is employed alone. The proportion of the former to the latter commonly varies from 1-6th to 1-4th. When ‘black malt’ is alone used, the proportion varies from the 1-10th to 1-15th. 1 lb. of ‘roasted malt,’ mashed with about 79 lbs. of pale malt, is said to be capable of imparting to the liquor the flavour and colour of porter. The following formulæ were formerly commonly employed in London:——

1. (DRAUGHT PORTER.) From pale malt, 3-1/2 q. s.; amber malt, 3 q. s.; brown malt, 1-1/2 q.; mash at twice with 28 and 24 barrels of water, boil with brown Kent hops, 56 lbs., and set with yeast, 40 lbs. _Prod._ 28 barrels, or 3-1/2 times the malt, besides 20 barrels of table-beer from a third mashing.

2. (BOTTLING PORTER; BROWN STOUT.) From pale malt, 2 q. s.; amber and brown malt, of each 1-1/2 qr.; mash at 3 times with 12, 7, and 6 barrels of water, boil with hops, 50 lbs., and set with yeast, 26 lbs. _Prod._ 17 barrels, or 1-1/2 times the malt.

The purity and quality of porter, as well as of other malt liquors, may be inferred in the manner noticed under BEER; but can only be positively determined by a chemical examination. For this purpose several distinct operations are required:——

1. _Richness in_ ALCOHOL. This may be correctly found by the method of M. Gay-Lussac; or from the boiling point. (See ALCOHOLOMETRY and EBULLIOSCOPE.) The method with anhydrous carbonate of potassa will also give results sufficiently near to the truth for ordinary purposes, when strong or old beer is operated on. The quantity of the liquor tested should be 3600 water grains measure; and it should be well agitated, with free exposure to the air, after weighing it, but before testing it for its alcohol. The weight of alcohol found, multiplied by 1·8587, gives its equivalent in sugar. This may be converted into ‘brewer’s pounds’ or density per barrel, as below.

2. _Richness in_ SACCHARINE or EXTRACTIVE MATTER. A like quantity of the liquor under examination, after being boiled for some time to dissipate its alcohol, is made up with distilled water, so as to be again exactly equal to 3600 water-grains measure. The sp. gr. of the resulting liquid is then taken, and this is reduced to ‘brewers’ pounds’ per barrel, by multiplying its excess of density above that of water (or 1000) by 360, and pointing off the three right-hand figures as decimals.

3. ACETIC ACID or VINEGAR. This is determined by any of the common methods of ACIDIMETRY (which _see_; see also ACETIMETRY). Each grain of anhydrous acetic acid so found represents 1·6765 gr. of sugar.

4. _Gravity of_ ORIGINAL WORT. This is obtained by the addition of the respective quantities of saccharine matter found in Nos. 1, 2, and 3 (_above_). These results are always slightly under the true original density of the wort, as cane sugar appears to have been taken by the Excise as the basis of their calculations. More correctly, 12% of proof spirit is equivalent to 19 lbs. of saccharine per barrel. 10-1/2 lbs. of saccharine are equiv. to 1 gall. of proof spirit.

5. _Detection of_ NARCOTICS. This may be effected either by the method described under ALKALOID, or by one or other of the following processes:——

_a._ Half a gallon of the beer under examination is evaporated to dryness in a water bath; the resulting extract is boiled for 30 or 40 minutes in a covered vessel with 10 or 12 fl. oz. of alcohol or strong rectified spirit, the mixture being occasionally stirred with a glass rod, to promote the action of the menstruum; the alcoholic solution is next filtered, treated with a sufficient quantity of solution of diacetate of lead to precipitate colouring matter, and again filtered; the filtrate is treated with a few drops of dilute sulphuric acid, again filtered, and then evaporated to dryness; it may then be tested with any of the usual reagents, either in the solid state, or after being dissolved in distilled water. Or the extract, obtained as above, may be boiled as directed with rectified spirit, the solution filtered, the spirit distilled off, and a small quantity of pure liquor of potassa added to the aqueous residue, which is then to be shaken up with about 1 fl. oz. of ether; lastly, the ethereal solution, which separates and floats on the surface, is decanted, evaporated, and the residuum tested, as before. The alkaline liquid, from which the ether has been decanted, is then separated from any precipitate which may have formed, and both of these separately tested for alkaloids.

_b._ From 2 to 3 oz. of purified animal charcoal are diffused through 1/2 gall. of the beer, and is digested in it, with frequent agitation, for from 8 to 12 hours; the liquor is next filtered, and the charcoal collected on the filter is boiled with about 1/2 pint of rectified spirit; the resulting alcoholic solution is then further treated as above, and tested. This answers well for the detection of strychnia or nux vomica.

6. PICRIC ACID. This substance, which was formerly employed to impart bitterness to London porter in lieu of hops, may be detected as follows:——

_a._ A portion of the liquor agitated with a little solution of diacetate of lead loses its bitter flavour if it depends on hops, but retains it if it depends on picric acid.

_b._ Pure beer is decoloured and deodorised by animal charcoal; but beer containing picric acid, when thus treated, retains a lemon-yellow colour and the odour.

_c._ Unbleached sheep’s wool, boiled for six or ten minutes, and then washed, takes a canary-yellow colour if picric acid be present. The test is so delicate that 1 grain of the adulterant in 150,000 gr. of beer is readily detected.

_d._ (Vitate.[117]) The author agitates 10 c.c. of the suspected beer in a test tube with half its volume of pure amylic alcohol. If the mixture is left to settle, the amylic stratum separates entirely, and is drawn off with a pipette, evaporated to dryness at a convenient temperature in a porcelain capsule, and the residue is finally taken up in a little distilled water with the aid of heat. The aqueous solution is divided into portions, and submitted to the following reagents. One portion is treated with a solution of ammonio-sulphate of copper, which, in dilute solutions of picric acid, instantly produces a turbidity, due to the formation of very minute crystals of the ammonio-picrate of copper, of a greenish colour. Another portion may be treated with a concentrated solution of cyanide of potassium, which produces a blood-red colour, more or less intense, according to the quantity of picric acid present, in consequence of the formation of iso-purpuric acid. A third portion may be submitted to the action of sulphide of ammonium, rendered still more alkaline by the addition of a few drops of ammonia. Here also a blood-red colour is produced, which becomes more intense on the application of heat, and is due to the formation of picramic acid.

[Footnote 117: ‘Chemical News,’ vol. xxxv, p. 75.]

7. MINERAL MATTER.——_a._ A weighed quantity of pure beer evaporated to dryness, and then incinerated, does not furnish more than from ·20% to ·35% of ash, the quantity varying within these limits with the strength of the liquor and the character of the water used in brewing it.

_b._ A solution of this ash, made by decoction with distilled water, should be only rendered slightly turbid by solutions of acetate of lead, bichloride of platinum, nitrate of baryta, nitrate of silver, oxalate of ammonia, and sulphuretted hydrogen.

_c._ If the beer contained common salt, the above solution will give a cloudy white precipitate with a solution of nitrate of silver. Each grain of this precipitate is equivalent to 1/2 gr. of common salt (nearly).

_d._ If GREEN COPPERAS (sulphate of iron) is present, ferridcyanide of potassium gives a blue precipitate, and ferrocyanide of potassium a bluish-white one, turning dark blue in the air; solution of chloride of barium gives a white precipitate, each grain of which, after being washed, dried, and ignited, represents 1·188 gr. of crystallised protosulphate of iron.

_e._ The ash, digested in water slightly acidulated with nitric acid, and then boiled, yields a solution which, when cold, gives a black precipitate with sulphuretted hydrogen, and a white one with dilute sulphuric acid when lead is present.

8. _Wittstein’s method for the detection of_ ADULTERANTS _in beer_.[118] One litre of the suspected beer is evaporated by a moderate heat to the consistence of a thick syrup. This is poured into a tared glass cylinder capable of containing ten times its volume and weighed; five times its weight of 93° to 95° alcohol is added, and the whole frequently stirred, by means of a thick glass rod, during twenty-four hours.

[Footnote 118: ‘Archiv der Pharmacie,’ January, 1876, (‘Pharm. Journal,’ 3rd series, v.)]

By this means all the gum, dextrin, sulphates, phosphates, and chlorides are separated, and a comparatively small portion is obtained in solution. After clearing, this solution is decanted, the residue is again treated with fresh alcohol, the two products mixed, filtered, and the alcohol driven off by a gentle heat.

_a._ Of the syrupy residue left after this evaporation, a small portion is diluted with three times its bulk of water, and tested for picric acid, according to the directions already given.

_b._ The remaining largest portion of the syrup is agitated for some time with six times its weight of pure colourless benzol (boiling point 80° C.); this is decanted off, and the operation is repeated with fresh benzol, and the two liquors, the first of which has become yellow, the second having scarcely changed colour, are evaporated at a gentle heat. The pale, yellow, resinous residue thus obtained may possibly contain brucine, strychnine, colchicine, or colocynthin. To ascertain this, three portions of the resin are placed on a porcelain capsule; one is treated with nitric acid (sp. gr. 1·33 to 1·40), another with concentrated sulphuric acid, and the third, after a few morsels of red chromate of potash have been added, also with sulphuric acid. A red colour, produced by the nitric acid, indicates brucine with certainty, and a violet colour colchicine; a red colour produced by sulphuric acid indicates colocynthin, and a purple violet, produced by sulphuric acid and bichromate of potash, reveals strychnine. Resin in which one or other of these colorations is produced possesses an extremely bitter taste; that in which the coloration does not take place is also bitter, but the bitterness recalls the well-known hop flavour.

_c._ The syrup which has been treated with benzol is freed, by gentle heating, from the small quantity of benzol remaining, and agitated twice with pure colourless amylic alcohol (boiling point 132° C.). The first portion of the alcohol acquires a more or less wine or golden-yellow colour. It would take up any picrotoxin or aloes if present, and thereby acquire a strongly bitter taste.

If neither of these two substances be present, the amylic alcohol does not become bitter, because neither the hop bitter nor the remaining four bitter principles——absinthin, gentipicrin, menyanthin, and quassiin——are soluble in it.

In order to distinguish picrotoxin from aloes a portion of the first obtained amylic alcoholic solution is poured upon glass, and allowed to evaporate spontaneously. If a fine white crystallisation be formed picrotoxin is present, if not aloes is present, and can only be recognised by its peculiar, saffron-like odour.

_d._ The syrup which has been treated with benzol and amylic alcohol is freed by means of blotting paper from the small quantity of amylic alcohol adhering to it, evaporation by heat being impracticable in consequence of the high boiling point of the alcohol, and shaken with anhydrous ether. This takes up the hop bitter yet present and absinthin. After evaporation the latter is easily recognised through its wormwood-like aroma; it also gives a reddish-yellow solution with concentrated sulphuric acid, which changes quickly to an indigo-blue colour.

_e._ After treating with ether the syrup has yet to be tested for gentipicrin, menyanthin, and quassiin. As it is now free from the hop bitter, a decidedly bitter taste points to one of these three substances. Any remaining ether is removed, and the syrup is dissolved in water and filtered; to one portion is added strong ammoniacal solution of silver, and it is then heated.

If it remains clear quassiin is present; if a silver mirror be formed it originates either with gentipicrin or menyanthin. Another portion is evaporated to dryness on porcelain, and concentrated sulphuric acid added. If, while cold, no change of colour takes place, but on heating it becomes carmine red, gentipicrin is present; menyanthin would give a yellowish-brown colour, gradually changing to violet.

For further information connected with this subject, see ALCOHOLOMETRY, ALE, BEER, BREWING, MALT LIQUORS, &c.

=PORT-FIRE.= A paper tube, from 9 to 12 inches in length, filled with a slow-burning composition of metal powder, nitre, and sulphur, rammed moderately hard, by a similar process to that adopted for small rockets. It is used in lieu of a touch-match, to fire guns, mortars, pyrotechnical devices, &c.

=PORTLAND CEMENT.= A species of mortar formed by calcining a mixture of limestone and argillaceous earth, and grinding the calcined mass to powder, in which state it must be preserved from the air. It is characterised by absorbing a large quantity of water, and then rapidly becoming solid, and, after a time, acquiring considerable hardness. See MORTAR and CEMENT.

=POSOL′OGY.= See DOSE.

=POS′SET.= _Syn._ POSSETUM, L. Milk curdled with wine or any other slightly acidulous liquor. It is usually sweetened with either sugar or treacle, and is taken hot.

_Prep._ From new milk, 1/2 pint; sherry or marsala, 1 wine-glassful; treacle, 1 or 2 tablespoonfuls, or q. s.; heat them together in a clean saucepan until the milk coagulates. This is called ‘treacle posset’ or ‘molasses posset,’ and, taken on retiring to rest, is highly esteemed in some parts of the country as a domestic remedy for colds. Lemon juice, strong old ale, or even vinegar, is occasionally substituted for wine, and powdered ginger or nutmeg added at will.

=POT METAL.= See COCK METAL.

=POT′ASH.= The ‘potash,’ or ‘potashes’ of commerce is an impure carbonate of potassium, so named after the pots or vessels in which it was first made. The ‘potash,’ or ‘potassa,’ of the chemist is the hydrate of a peculiar metal, potassium, which is more particularly referred to below. The word potash is vulgarly applied to the crude or commercial carbonate of potassium. See CARBONATE OF POTASSIUM, &c.

Potash is now principally obtained from the following sources:——

1. From carnallite,[119] a hydrated double chloride of potassium and magnesium, which occurs associated with other salts of potassium and magnesium, as well as of sodium, in a bed of clay, at Stassfurth, near Madgeburg, in Prussia.

[Footnote 119: Carnallite contains nearly a fourth of its weight of potassium chloride.]

2. Feldspar and similar minerals.

3. Sea water, and the mother-liquor of salt works.

4. Native saltpetre.

5. The ashes of several plants.

6. The calcined residue of the molasses of beet-root sugar remaining after distillation.

7. The seaweeds, as a by-product of the manufacture of iodine.

8. From the fleece of the sheep.[120]

[Footnote 120: Maumené and Rogelet state that a fleece weighing 9 lbs. contains about 6 ounces of pure potash.]

The following is a process for obtaining alkali from seaweed, described in the ‘Chemical News’ for Nov. 10th, 1876:——

At the chemical works at Aalbourg, in Jutland, Denmark, where about 30 tons of alkali are made per week by the ammonia process, Mr Theobald Schmidt, the director of the manufactory, proposes to work, in conjunction with this process, a method devised by himself of treating seaweed so as to obtain iodine, potash, salts, and other marketable products therefrom.

In Denmark a very heavy duty is levied on the importation of common salt, whilst enormous quantities of seaweed rich in iodine and potash can be obtained at small cost in the neighbourhood of the works. Mr Schmidt’s process is as follows:——After the seaweed is dried and burnt, a concentrated solution of the ash is made and added to the liquor, containing chlorides of sodium and calcium, left after the ammonia has been recovered in the ammonia-soda process by boiling with lime. The sulphates of potash, soda, and magnesia, contained in the ash of the seaweed are thereby decomposed, and hydrated sulphate of lime and hydrated magnesia are precipitated in a form which may be available for paper-making, as ‘pearl-hardening.’ The last traces of sulphates are got rid of by adding a small quantity of solution of chloride of barium. To the clear solution nitrate of lead is now added, until all the iodine is precipitated as iodide of lead, which is then separated by filtration and treated for the production of iodine or iodides. After filtration the liquid is boiled; nitrate of soda is added to convert the chloride of potassium present into nitrate of potash. The latter is separated by crystallisation. There remains a solution of common salt, containing traces of ammonia from the previous soda operation, and a trace of chloride of potassium. This solution is again treated by the ordinary ammonia-soda process for the production of bicarbonate of soda and white alkali. See CARBONATE OF POTASSIUM, &c.

=POTAS′SIUM.= K. The metallic base of potash. It was discovered, in 1807, by Sir H. Davy, who obtained it by submitting moistened potassium hydrate, under a film of naphtha, to the action of a powerful voltaic current. It has since been procured by easier methods, of which the following, invented by Brunner, is the best.

_Prep._ An intimate mixture of carbonate of potassium and charcoal is prepared by calcining, in a covered iron pot, the crude tartar of commerce; when cold, it is rubbed to powder, mixed with 1-10th part of charcoal in small lumps, and quickly transferred into a retort of stout hammered iron; the latter may be one of the iron bottles in which quicksilver is imported, a short and somewhat wide iron tube having been fitted to the aperture; the retort, thus charged, is placed upon its side, in a furnace so constructed that the flame of a very strong fire, preferably fed with dry wood, may wrap round it, and maintain every part of it at a very high and uniform degree of heat. A copper receiver, divided in the centre by a diaphragm, is next connected to the iron pipe, and kept cool by the application of ice, whilst the receiver itself is partly filled with mineral naphtha, to preserve the newly formed potassium as it distils over. The arrangement of the apparatus being completed, the fire is gradually raised until the requisite temperature, which is that of full whiteness, is reached, when decomposition of the alkali by the charcoal commences, carbonic acid gas is abundantly disengaged, and potassium distils over, and falls in large drops into the liquid. To render the product absolutely pure, it is redistilled in an iron or green-glass retort, into which some naphtha has been put, that its vapour may expel the air, and prevent the oxidation of the metal. The pieces of charcoal are introduced for the purpose of absorbing the melted carbonate of potassium and preventing its separation from the finely divided carbonaceous matter. _Prod._ 3% to 4% of the weight of tartar acted on; 1 lb. yielded 280 gr.

_Prop., &c._ Pure potassium is a brilliant white metal, with a high lustre; at the common temperature of the air it is soft, and may be easily cut with a knife, but at 32° Fahr. it is brittle and crystalline; it melts completely at 136° Fahr., and in close vessels distils unaltered at a low red heat. Sp. gr. ·865. Its most remarkable property is its affinity for oxygen, which is so great that it takes it from most other substances containing it. Exposed to the air, its surface is instantly tarnished, and quickly becomes covered with a crust of oxide or hydrate. It inflames spontaneously when thrown on water, and burns with a beautiful purple or purple-red flame, yielding a pure alkaline solution. It can only be preserved in naphtha, rock oil, or some other fluid hydrocarbon.

The salts of potassium are all soluble in water, the tartrate, periodate, and fluosilicate being the least so; they are usually colourless, unless the acid be coloured, crystallise readily, and form numerous double compounds. They can be recognised as follows:——

Sulphuretted hydrogen, sulphide of ammonium, and carbonate of ammonium, do not affect them. A solution of tartaric acid, added in excess, to moderately strong neutral or alkaline solutions of potassium salts, gives a quickly subsiding, gritty or crystalline, white precipitate, which is redissolved on heating the liquid, and again separates as it cools; and is also soluble in aqueous solutions containing free alkali, or free mineral acids. Platinic chloride produces, in neutral and acid solutions, a yellow crystalline precipitate. Alkaline solutions require to be first slightly acidulated with hydrochloric acid. The separation of the precipitate here, as well as that produced by tartaric acid, is promoted by violent agitation and friction against the sides of the vessel, and the delicacy of both is increased by the addition of some alcohol. When converted into carbonate by igniting with excess of carbonate of ammonium and alcohol, and treated with sulphuretted hydrogen solution and nitro-prusside of sodium, gives a splendid violet colour, turning through red to green on standing.

Potassium salts give with sodium periodate and hydro-fluosilicic acid white precipitates soluble in much water.

Heated in the inner flame of the blow-pipe on platinum wire, they impart a violet coloration, masked, however, by a mere trace of sodium salts.

=Potassium, Acetate of.= KC_{2}H_{3}O_{2}. _Syn._ ACETATE OF POTASH, POTASSIC ACETATE; POTASSÆ 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 potassium, 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 potassium, prepared as above, occurs in shining white masses, 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 potassium. 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 88·8 gr. of sulphate of potassium.

_Uses, &c._ Acetate of potassium 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 potassium in the system.——_Dose._ As a diaphoretic and antiscorbutic, 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.

=Potassium Antimoniates.= The normal potassic antimoniate may be obtained by heating, in an earthen crucible, 1 part of metallic antimony with 4 parts of nitrate of potash. The mass so obtained is reduced to powder, and afterwards washed with warm water to remove the excess of potash and potassic 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 potassium. 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 potassium (K_{2}Sb_{4}O_{11}.) may be procured by passing a stream of carbonic anhydride through a solution of the normal antimoniate.

Acid metantimoniate of potash, or hydro-potassic metantimoniate is prepared as follows:——Potassic 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 glass 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.

=Potassium, Arseniate of.= KH_{2}AsO_{4}. _Syn._ ARSENIATE OF POTASSA, MONOPOTASSIC ARSENIATE, POTASSIUM DIHYDRIC ARSENIATE; POTASSÆ BINARSENIAS, L. _Prep._ Take of arsenious acid (white arsenic) and nitrate of potassium, of each, in powder, 1 part; heat the mixture to dull redness in a glass 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.

=Potassium, Borate of.= K_{4}B_{4}O_{8}. _Syn._ POTASSÆ BORAS, L. _Prep._ From dry carbonate of potassium and dry boracic acids, equal parts, reduced to powder, and heated to redness in a covered crucible; the sublimed mass, 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.

=Potassium, Borotartrate of.= _Syn._ POTASSÆ BOROTARTRAS, CREMOR TARTARI SOLUBILIS, L.; CRÈME DE TARTRE SOLUBLE, Fr. _Prep._ (P. Cod.) Crystallised boracic acid, 1 part; bitartrate of potassium, 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.

=Potassium, Bromide of.= KBr. _Syn._ POTASSII 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.

=Potassium, Carbonate of.= K_{2}CO_{3}. _Syn._ CARBONATE OF POTASSA, SUBCARBONATE OF POTASSA, SALT OF TARTAR; POTASSÆ CARBONAS (B. P., Ph. L., E., D.). Impure or crude carbonate of potassium is chiefly imported from America and Russia, and is obtained by lixiviating wood ashes, and evaporating the solution to dryness. The mass 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 constitutes 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 mass, which is kept constantly stirred by means of an iron rod. The ignition is continued until the impurities are burned out, and the mass 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 constitutes ‘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 assiduously stirred, so that it may form small white granulations, instead of adhering together to form an amorphous solid mass. In this state it constitutes the ordinary or carbonate of potassa of the Pharmacopœias. 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 mass 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 quantity of cold distilled water; the new solution, after filtration, is again evaporated to dryness. The product is quite free from potassium sulphate, and is nearly free from both potassium chloride and silicates.

=Potassium, Pure Carbonate of.= CARBONATE OF POTASSA (POTASSÆ CARBONAS PURUM——Ph. E. & D., and Ph. L., 1836).——(Ph. L., 1836.) From bicarbonate of potassium, in crystals, heated to redness in a crucible.

(Ph. E.) As the last. Or, more cheaply, by dissolving bitartrate of potassium 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 mass, 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 potassium, 2 lbs., is exposed to a red heat in an iron crucible, as before; the powdered calcined mass 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 potassium, 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 potassium frequently contains an undue quantity 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 potassium 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 26·3 gr. of carbonate anhydride when placed in contact with dilute sulphuric acid.

=Potassium, Bicarbonate of.= KHCO_{3}. _Syn._ POTASSIUM HYDROGEN CARBONATE, BICARBONATE OF POTASSA; POTASSÆ BICARBONAS (B. P., Ph. L., E., & D.). _Prep._ 1. (Ph. L. 1836.) Carbonate of potassium, 6 lbs.; distilled water, 1 gall.; dissolve, and pass 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 passed, by means of glass tubes connected by vulcanised india rubber, to the bottom of a bottle containing a solution of carbonate of potassium, 1 part, in water, 2-1/2 parts; as soon as the air is expelled from the apparatus the corks through which the tubes pass 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 potassium 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.) Potassium 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 potassium may be obtained; next dissolve carbonate of potassium, 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 potassium, 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 mass towards the end of the process.

6. (Commercial.) From carbonate of potassium, 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 coke or charcoal, and purified by being forced through a cistern of cold water; the resulting salt is next dissolved in the least possible quantity 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 potassium, 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 potassium 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, 30·7 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 potassium is the most agreeable of all the salts of potassium, 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 potassium 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.

=Potassium, Chlorate of.= KClO_{3}. _Syn._ CHLORATE OF POTASH; POTASSÆ 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 potassium, 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 potassium. The mother-liquor, which contains much chloride of potassium 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 potassium consumed in it, according to the skill with which it is conducted; this apparent loss of potassium arises from a large portion of it being converted into chloride, a salt of comparatively little value. The following processes have been devised principally with the view of preventing this waste, or of employing a cheaper salt of potassium 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.