Chapter C: W. HEATON, F.I.C., F.C.S., Lecturer on Chemistry at the (9)

-----------------------+-------+-------------------------------------------+
| | B |
| |--------------------^----------------------+
NAMES, &c | | C | | | |
| |------^--------| | | |
| A | D | E | F | G | H |
-----------------------+-------+------+--------+---------+--------+--------+
AMMONIA | | | | | | |
(pure, gaseous) | ·77273| 7·727| 7-3/4 | 19-1/3 | 38-5/8 | 77-3/0 |
| | | | | | |
Carbonate of ammonia | | | | | | |
(neutral, anhydrous) |1·77273|17·727|17-3/4 | 44-5/16 | 88-5/8 |177-1/4 |
| | | | | | |
Carbonate of ammonia | | | | | | |
(neutral, | | | | | | |
crystallised) |1·9773 |19·773|19-3/4 | 49-7/16 | 98-7/8 |197-3/4 |
| | | | | | |
Sesquicarbonate of | | | | | | |
ammonia (translucent) |2·6818 |26·818|26-13/16| 67-1/10 |134-1/10|268-1/5 |
| | | | | | |
Bicarbonate of ammonia | | | | | | |
(crystallised) |3·5909 |35·909|35-9/10 | 89-13/16|179-5/8 |359-1/10|
| | | | | | |
POTASSA (anhydrous) |2·1364 |21·364|21-1/2 | 53-1/2 |107 |213-3/8 |
| | | | | | |
Hydrate of potassa |2·54546|25·455|25-5/11 | 63-5/8 |127-1/4 |254-1/2 |
| | | | | | |
Carbonate of potassa | | | | | | |
(anhydrous) |3·1364 |31·364|31-3/8 | 78-1/2 |157 |313-1/2 |
| | | | | | |
Carbonate of potassa | | | | | | |
(granulated) |3·7727 |37·727|37-1/2 | 94-3/10 |188-5/8 |377-1/4 |
| | | | | | |
Carbonate of potassa | | | | | | |
(crystallised) |3·9545 |39·545|39-5/8 | 99 |198 |395-1/2 |
| | | | | | |
Bicarbonate of potassa | | | | | | |
(crystallised) |4·5454 |45·454|45-1/2 |113-3/4 |227-1/2 |454-1/2 |
| | | | | | |
SODA (anhydrous) |1·4091 |14·09 |14-1/10 | 35-1/4 | 70-1/2 |141 |
| | | | | | |
Hydrate of soda |1·8182 |18·182|18-1/5 | 45-1/2 | 91 |182 |
| | | | | | |
Carbonate of soda | | | | | | |
(anhydrous) |2·4091 |24·091|24-1/10 | 60-1/4 |120-1/2 |241 |
| | | | | | |
Carbonate of soda | | | | | | |
(crystallised) |6·5 |65· |65 |162-1/2 |325 |650 |
| | | | | | |
Sesquicarbonate of soda| | | | | | |
(dry; theoretical) |2·9091 |29·091|29-1/10 | 72-1/2 |145 |290 |
| | | | | | |
Sesquicarbonate of | | | | | | |
soda (Ph. L., 1836) |3·7273 |37·273|37-1/4 | 93-1/4 |186-1/2 |373 |
| | | | | | |
Sesquicarbonate of | | | | | | |
soda (average | | | | | | |
commercial) |3·7954 |37·954|38 | 94-7/8 |189-3/4 |379-1/2 |
| | | | | | |
Bicarbonate of soda | | | | | | |
(crystallised) |3·8182 |38·182|38-1/5 | 95-1/2 |191 |382 |
| | | | | | |
LITHIA (pure, | | | | | | |
anhydrous) | ·6818 | 6·818| 6-13/16| 17-1/20 | 34-1/10| 68-1/5 |
| | | | | | |
BARYTA (pure, | | | | | | |
caustic) |3·4773 |34·773|34-4/5 | 86-7/8 |173-7/8 |347-3/4 |
| | | | | | |
LIME (pure, caustic) |1·2727 |12·727|12-3/4 | 31-3/4 | 63-5/8 |127-1/4 |
| | | | | | |
MAGNESIA (pure, | | | | | | |
anhydrous) | ·90909| 9·091| 9-1/11 | 22-3/4 | 45-1/2 | 91 |
-----------------------+-------+------+--------+---------+--------+--------+

In this ingenious method of alkalimetry it is absolutely necessary that the whole of the alkali in the specimen tested should be in the state of neutral carbonate. If a sample of potash contains any caustic alkali (as the potashes and pearlash of commerce generally do), Fresenius and Will direct it, previously to being tested, to be triturated with its own weight of pure quartzose sand, and about one third of its weight of carbonate of ammonia; and the resulting mixture, placed in a small iron capsule, or a porcelain crucible, to be moistened with water, and exposed to a gentle heat until it becomes quite dry, and all the ammonia is expelled. If the sample contains any bicarbonate or sesquicarbonate, it must be heated to dull redness before being placed in the apparatus and tested. In the case of crude soda (particularly soda ash), the proportion of carbonate of ammonia should be equal to at least one half the quantity operated on. With both alkalies, if the sample contains sulphides, sulphites, or hyposulphites, the same method is to be followed, except that solution of ammonia, instead of water, is to be employed for moistening the powder. To remedy the error which would arise from the apparent amount of carbonic anhydride liberated during the assay, being swelled by the disengagement of 'sulphuretted hydrogen' or sulphurous acid from these substances, a small quantity of neutral (_i. e._ yellow) chromate of potash may be added to the alkaline solution in the flask (_A_); by which they will be converted into sulphates, sulphur, and water, which will remain in the apparatus, the carbonic acid only being evolved. "As most sorts of soda of commerce contain one or other of the substances (just) named, and as it is far more simple to add at once some chromate of potassa to the soda solution, than to test the latter for either of the three salts, it is always advisable to make it a rule, in the examination of SODA, to add some chromate of potassa." (Fresenius.)

If the sodium or other carbonate under analysis contains much chloride, the addition of more sulphuric acid than necessary must be avoided, and the carbonic anhydride expelled by gently heating over a warm bath, and not by the addition of excess of acid.

To obviate the difficulties, and to give greater precision and delicacy to volumetrical assays, the instrument known as Mohr's ALKALIMETER, or Mohr's BURETTE, and which is figured in the margin, may be employed. By means of it the test-acid in the graduated tube (_a_) may be added to the alkaline solution in (_f_), in any quantity at a time, however minute, by merely pressing the handles of the clamp (_d_) with the thumb and finger. The terminal tube (_e_) has its lower orifice very small, and it is connected with the burette by means of a small piece of vulcanised india-rubber tube, on which the clamp (_d_) acts. (See _engr._) The inner cylindrical part of the arm (_b_) is lined with cork, to prevent injury to the glass burette, and to hold it the more firmly.

Generally the alkali in the specimen examined may be in either the caustic or carbonated state, or it may consist of any mixture of caustic alkali, or carbonates; but it is absolutely necessary for accurate results, that it should be free from sulphides, sulphites, and hyposulphites, as sulphuric acid acts upon these substances as well as on carbonates. The presence of chlorides does not interfere with the accuracy of the assay, unless a higher degree of heat is employed than that necessary for the expulsion of the absorbed carbonic acid. The SODA-ASH of commerce generally contains all these substances besides common salt, sulphate of soda, and insoluble matter, which do not interfere. Rough samples of POT-ASHES and PEARL-ASH also generally contain some sulphides, though not a large quantity. Various plans have been proposed to avoid this source of error. The best is that of MM. Fresenius and Will, given above, in which the value of the carbonates is estimated by their yield of carbonic anhydride.

The difference between an assay of a sample of the unprepared alkali and of another which has been treated as above, indicates the quantity of impurities contained in them under the forms just referred to. The presence of these substances in the commercial alkalies may be detected by the following tests:--

_Sulphides._ The addition of sulphuric acid causes the evolution of an odour like that of rotten eggs. The sample in solution yields a black precipitate with acetate of lead. But the most delicate test is the splendid violet-blue colour with nitro-prusside of sodium.

_Sulphites and Hyposulphites._ A solution of the alkali, insufficient for saturation, being added to sulphuric acid tinged reddish yellow with bichromate of potash, occasions a greenish tinge (owing to the formation of oxide of chromium), when these are present. Hydrochloric acid added to a clear solution, after some time, causes a turbidity and odour of sulphurous anhydride.

_Chlorides_ yield a copious curdy precipitate with nitrate of silver, soluble in ammonia, and reprecipitated by excess of nitric acid.

The amount of pure caustic alkali in a sample of alkali is best determined by Fresenius's method, as follows:--The total amount of pure alkali, both caustic and carbonated, expressed in per-cents. of carbonate of soda or carbonate of potassa, is ascertained by any of the usual methods. The apparent quantity of alkali per cent. is then determined, without previous treatment of the sample with carbonate of ammonia, by the method of Will and Fresenius (p. 86). The difference between the results indicates the per-centage of dry caustic alkali present; or if the volumetric method be in use, it can be often fairly estimated by adding the first portions of the test-acid very gradually to the sample, carefully observing the effect. When the effervescence at length commences the weight or measure of the test-liquor expended shows the quantity of pure caustic alkali under treatment (nearly). The result depends upon the fact, that little or no carbonic-acid gas is expelled from the liquid on the addition of the test-acid, until the caustic portion is very nearly neutralised.

The quantity of WATER or MOISTURE, per cent., present in an alkaline carbonate, is indicated by the loss of weight which 100 gr. suffer on gentle ignition in a loosely-covered iron dish or platinum crucible. So also with samples containing caustic alkali, except that here the water of hydration (= 1 equiv. = 9) is not expelled from the 'caustic' portion, and must therefore be determined by calculation.

Other matters deserving the serious attention of the operator are--hitting the exact point of neutralisation, and--preparing the test-acids of the proper strength. The method of effecting the former correctly has been already referred to in this article, and is also fully noticed under ACETIMETRY and ACIDIMETRY.

_Test-acids_ may be very simply prepared by gradually diluting concentrated sulphuric acid with water until it is reduced to the proper strength; the dilution being made in a glass vessel containing a 'hydrostatic bead' exactly corresponding to the desired specific gravity of the dilute acid. When the proper point is reached, and the mixture has again acquired the normal temperature of 60° Fahr., the bead rises from the bottom of the vessel, and floats about indifferently in the middle of the liquid. The sp. gr. may then he carefully ascertained by means of an hydrometer or a specific gravity bottle; after which the strength must be accurately determined by means of a standard solution of either pure anhydrous carbonate of soda or pure caustic soda. An acid of any given strength or saturating power may also be prepared in the following manner:--49 parts of commercial sulphuric acid (oil of vitriol), sp. gr. 1·825, contain nearly 40 parts or 1 equiv. of anhydrous sulphuric acid; if we, therefore, wish to prepare a dilute acid containing in every 1000 grains weight, or measure, exactly 1 equiv. of hydrated sulphuric acid, we have only to make 49 gr. of such acid up to 100 gr. weight or measure with pure water. After it has recovered the proper temperature, its sp. gr., or rather its saturating power, must be carefully tried, and, if necessary, readjusted. As, however, it very often happens that the oil of vitriol employed is not so strong as that above referred to, it is better first to test its strength with pure anhydrous carbonate of soda, and to calculate the quantity required by the Rule of Proportion. Every 53 gr. of the dry carbonate are equal to 40 gr. of 'dry sulphuric acid.' Suppose we find the oil of vitriol to contain only 72% of hydrated acid, then--

100 : 40 :: 72 : 55·55

or, instead of only 40 gr., fully 55-1/4 gr. will be required, which are to be made up with water to 1000 gr., as before. Finally, the diluted acid must be very carefully re-tested, and if found correct, at once put into a well-stoppered bottle, and labelled, for use. Too much care cannot be taken to ensure the test-liquid, whether for alkalies or acids, being of the proper strength, of which the specific gravity alone is an insufficient proof. In practice, so small a quantity only of test-acid as that referred to above is, of course, seldom made; but as any larger quantities are mere multiples of the smaller one, the necessary proportions to be employed are easily calculated. The common plan is to prepare one or more gallons or quantities of 10 lbs. each, and to preserve the liquid in stoppered green glass 'Winchester-quart bottles,' so that it may be always ready for use.

Although, as may be inferred from the text, sulphuric acid is generally used as the standard acid, yet oxalic acid in pure crystals is recommended by M. Mohr, and answers admirably, and is prepared and used exactly in the same manner.

TABLE II.--_Alkalimetrical Equivalents._

Grains.
{ 17 AMMONIA (pure or gaseous).
{ 43-1/2 Carbonate of ammonia
{ (neutral, hydrated).
{ 59 Sesquicarbonate of ammonia
{ (Ph. L.; translucent, hydrated).
{ 79 Bicarbonate of ammonia
{ (crystallised).
{ 47 POTASSA (anhydrous).
{ 56 Hydrate of potassa (pure
{ caustic potassa).
{ 69 Carbonate of potassa
{ (anhydrous).
{ 83 " " (granulated,
{ commercial).
{ 87 " "
{ (crystallised).
{100 Bicarbonate of potassa
{ (crystallised).
Grains { 31 SODA (anhydrous).
22 Carbonic anhydride } { 40 Hydrate of soda (pure caustic
(dry). } { soda).
63 Oxalic acid } { 53 Carbonate of soda (anhydrous).
(crystallised). } {143 " " (crystallised).
49 Sulphuric acid } are { 84 Bicarbonate of soda
(liquid, }equivalent{ (crystallised).
monohydrated, } to { 83-1/2 Sesquicarbonate of soda
sp. gr. 1·8485). } { (average commercial).
75 Tartaric acid } { 84 Bicarbonate of soda (crystals,
(crystallised). } { or cryst. powder,
1000 Dilute sulphuric acid} { free from moisture).
(sp. gr. 1·033). } { ============
} {
Water--gr. measure. } { 15 LITHIA.
1000 Dilute sulphuric } { 24 Hydrate of lithia.
acid (sp. gr. 1·032). } { 37 Carbonate of lithia.
{ ============
{ 76-1/2 BARYTA (pure, caustic).
{ 85-1/2 Hydrate of baryta.
{ 98-1/2 Carbonate of baryta.
{ 28 LIME (pure, caustic;
{ _i. e._ quick-lime).
{ 37 Hydrate of lime (slaked lime).
{ 50 Carbonate of lime
{ (chalk; marble).
{ 20 MAGNESIA (pure, calcined).
{ 42 Carbonate of magnesia (dry,
{ neutral).
{ 48-1/2 " " (ordinary
{ commercial).
{ 52 STRONIA (pure, caustic).
{ 61 Hydrate of strontia.
{ 74 Carbonate of strontia.

=ALKALOID.= _Syn._ VEGETABLE ALKALI, ORGANIC BASE; ALKALOÏDES (_pl._, -IDES, or -IDÆ), L.; ALCALOÏDE, ALCALI ORGANIQUE, Fr. In _chemistry_, a name commonly given to any proximate principle of vegetable origin possessing alkaline or basic properties, however feeble. In its most extended sense the term embraces all organic bases, whether obtained from the animal or vegetable kingdom, or produced artificially. The alkaloids form a numerous and important class of bodies. They exist in nature nearly always in the form of salts, the acid being often, like themselves, peculiar to the plant, or class of plants, in which they are found; whilst the medicinal activity of the latter, in most cases, almost entirely depends on their presence.

_Prep._ The following general methods of procuring the alkaloids will be found applicable to such as full directions are not given for under their respective heads:--

1. (When the base is insoluble in water, non-volatile, and existing in the plant in an insoluble form.) The bruised plant is boiled or macerated in water acidulated with hydrochloric or acetic acid, and the liquor, after filtration, is neutralised with an alkali (ammonia, potassa, lime, or magnesia); the resulting precipitate is purified by re-solution in dilute acid, digestion with a little animal charcoal, and subsequent crystallisation, or re-precipitation with an alkali; or the first precipitate is purified by dissolving it once, or, if necessary, several times, in boiling alcohol, which yields the pure alkaloid either on cooling or by evaporation.

2. (When the base is insoluble in water, and non-volatile, but existing in the plant as a soluble salt.) The bruised or sliced plant is boiled or macerated in water, and the filtered liquor precipitated and otherwise treated as before.

3. (When the base is soluble in water, and non-volatile.) An infusion made with very dilute acid, hydrochloric or acetic, is concentrated by a gentle heat; and the residual liquor treated with potassa (or concentrated solution of ammonia) and ether conjointly; after repose, the ethereal solution is decanted and evaporated. For those alkaloids which are insoluble in ether (as morphia and cinchonia), the previous process may be adopted.

4. (When the base is both soluble in water and volatile.) The vegetable, in a bruised or divided state, or its extract, is alkalised with potassa and distilled; the distillate is neutralised with dilute oxalic or sulphuric acid, and carefully evaporated to dryness; the residuum is next digested in alcohol, and the resulting tincture agitated with potassa and ether, the former being in quantity just sufficient to seize on all the acid; lastly, the ethereal solution thus formed, on careful evaporation, leaves the alkaloid nearly pure. It may be further purified by cautious distillation.

As some of the alkaloids are soluble in excess of the alkaline precipitant, over-saturation should be carefully avoided; or the precipitant may be used under the form of carbonate or bicarbonate. When lime and magnesia are employed, they are boiled for a few minutes with the solution.

_Props._ Alcoholic or aqueous solutions of the alkaloids generally exhibit an alkaline reaction with vegetable colours. Like the alkalies, also, they combine with acids to form salts which, when dissolved in water, are capable of producing the ordinary phenomena of saline double decomposition. Their taste is usually intensely bitter.

The majority of the natural alkaloids contain carbon, hydrogen, nitrogen, and oxygen, and are, at ordinary temperatures, solid, and not volatile without decomposition. Some natural alkaloids contain carbon, hydrogen, and nitrogen only; these are, for the most part, liquid at ordinary temperatures, and can be distilled without decomposition. The greater number of the artificial alkalies are composed of carbon, hydrogen, and nitrogen; some, however, contain oxygen in addition. Alkaloids have also been obtained artificially, in which nitrogen is replaced by phosphorus, arsenic, antimony, or bismuth. Most of the alkaloids, as they are obtained in the free state, correspond in function to ammonia, NH_{3}, rather than to the fixed alkalies; that is to say, they form salts by direct union with acids, without elimination of water or any other substance. In order to make them strictly comparable to the fixed alkalies, they require, like ammonia, the addition of water (H_{2}O) to their formulæ; they may then be considered as hydrates of compound radicles analogous to ammonium.

_Physiological action._ The alkaloids generally possess great medicinal power; some of them act with terrific energy, and are the most violent poisons with which we are acquainted. Perfectly pure aconitia is about 200 times more poisonous than arsenic, and at least 50 times more poisonous than ordinary medicinal prussic acid. The greater number act on animals in the same way as the plants which produce them, provided they are given in proportionately small doses. Many of them, when judiciously administered, are most valuable medicines.

_Pois., Ant., &c._ Some of the alkaloids act as narcotic or stupefying poisons; others are classed with the narcotico-acrid poisons, or those which produce both narcotism and irritation of the parts they touch. The general symptoms produced by opium and its preparations may be taken as an example of the former; those from aconite and strychnia, of the latter. In large doses of the greater number, narcotism predominates; in smaller ones, irritation; they are rarely coexistent.--_Treatm._ No common antidote to the effects of this class of substances has yet been discovered. The only safe treatment, of at all general application, is to immediately clear the stomach by means of a strong and quick-acting emetic (as sulphate of zinc), or the stomach-pump, and to administer copious and continued draughts of astringent vegetable solutions (as of tannin, nut-galls, oak-bark, or what is always at hand--very strong tea or coffee). These may be followed by or combined with a smart purge of castor oil, as soon as the stomach is thoroughly cleared of the poison. M. Bouchardat strongly recommends a solution of iodine, 3 gr., and iodide of potassium, 6 gr., in pure water, 16 fl. oz., in cases of poisoning by OPIUM, ACONITE, COLCHICUM, DEADLY NIGHTSHADE, HEMLOCK, NUX VOMICA, &c., or by the alkaloids obtained from them--ACONITINE, ATROPIA, COLCHICINA, CONIA, MORPHIA, STRYCHNIA, &c., or their salts; but _not_ where foxglove or digitalin has been taken. The stomach having been well emptied by an emetic, the solution is to be given by wine-glassfuls for some time; the vomiting being still encouraged during the early part of the administration of the antidote. In the case of narcotics (as opium, morphia, &c.), this is to be followed by the free use of a strong infusion of coffee. According to Dr Garrod, purified animal charcoal is an 'excellent antidote' to many of the alkaloids, including those above enumerated, when taken in poisonous doses; as it not merely absorbs them, but, for the most part, renders them inert. To be serviceable it should be recently prepared and fresh-burnt; and should be given in doses of about an ounce at a time, diffused in warm or tepid water, and frequently repeated. The vomiting which follows its use, owing to the warm water, proves advantageous; but after a sufficient time may be lessened by employing less water, or cooler or even cold water. Drowsiness, if present, may be combated by the subsequent use of strong coffee or tea, as before. We have seen this plan succeed in several cases.--_Lesions._ These, like the symptoms, vary. In some cases there are redness and inflammation of the stomach and intestines, and turgescence of the vessels of the lungs and brain; in others, these appearances are either slight or wholly wanting. Wherever there has been much cerebral disturbance, traces of congestion are usually discernible.

_Detec., Tests, &c._ The identification of the pure alkaloids is extremely simple; but their detection, when combined with organic and colouring matters, is a task of considerable difficulty. One or other of the following plans may be adopted for this purpose:--

1. (Merck.) The matter under examination is digested, for several hours, with concentrated acetic acid, added in sufficient quantity to produce a strongly acid reaction; the fluid portion is then strained from the insoluble matter, and the latter being washed with water acidulated with acetic acid, the mixed liquors are gently evaporated to dryness in a water bath; the residuum of the evaporation is boiled first with rectified spirit, and next with rectified spirit acidulated with acetic acid; the mixed liquors are again evaporated, the residuum redissolved or diluted with distilled water, and carbonate of soda or potassa added to feebly alkaline reaction, and the whole, after evaporation to the consistence of a syrup, set aside to repose for 24 hours; it is now again diluted with water, filtered, and the insoluble portion washed with cold distilled water, and digested with concentrated acetic acid; this last solution is diluted with distilled water, and decoloured with pure blood-charcoal (if it be necessary); the fluid, either at once, or after cautious evaporation, may then be tested for the alkaloids, in the usual manner. The charcoal previously used should also be tested in the way described below. This method answers admirably with all the NON-VOLATILE ALKALOIDS, and may be applied to the stomach and viscera, and their contents, and to food, &c., in cases of poisoning.

2. (Stas.) The suspected matter, in a finely divided state, is digested, at 160° to 165° Fahr., with twice or thrice its weight of strong alcohol acidulated (according to the quantity) with 1/2 dr. to 2 or 3 dr., or more, of pure oxalic or tartaric acid. After a sufficient time, and when the whole has become quite cold, it is thrown on a filter, and the undissolved portion, after being squeezed dry, is washed with strong alcohol. The mixed and filtered alcoholic liquids are then evaporated at a temperature not exceeding 95° Fahr., and, if no insoluble matter separates, the evaporation is continued nearly to dryness;[19] but if fatty or other insoluble matter separates during the process of concentration, the concentrated fluid is passed through a moistened filter, and the filtrate evaporated nearly to dryness, as before. The residuum is next digested with absolute alcohol, in the cold, the insoluble portion, after filtration, washed with alcohol, and the mixed filtrates again evaporated in the air, or in vacuo. The acid residue is now dissolved in a little distilled water, and bicarbonate of soda added as long as effervescence ensues. To this mixture 4 or 5 times its volume of ether is added, and after lengthened agitation (the bottle or tube being held in a cold wet cloth), the whole is allowed to repose for a short time. A little of the supernatant ether is now removed to a small glass capsule or watch-glass, and allowed to evaporate spontaneously.[19] When this leaves oily streaks upon the glass, which gradually collect into a small drop, which emits, when gently heated, a disagreeable, pungent, and stifling odour, the presence of a LIQUID VOLATILE BASE or ALKALOID is inferred; whilst a solid residue or a turbid fluid with small solid particles floating in it, indicates a NON-VOLATILE SOLID BASE.[20] In either case the blue colour of reddened litmus is permanently restored by the residuum. If no residuum is left on the capsule, some solution of pure soda or potassa is added to the liquid, the whole well agitated for several minutes, and the ether (after repose) decanted; an operation which is repeated with fresh ether a second, third, and even a fourth time. The base, or bases (if any are present), will now be found in the mixed ethereal solution, which is, therefore, tested as before. The presence of an alkaloid being detected, the mixed ethereal solutions are allowed to evaporate spontaneously, care being taken, if a volatile alkaloid be present, to neutralise the liquid with an acid before the final evaporation. The last residuum is then tested for the particular alkaloid present, as before.[21]

[Footnote 19: The evaporation, according to Stas, should be conducted under a bell-glass over sulphuric acid, with or without rarefaction of the air; or in a tubular retort through which a current of air is made to pass.]

[Footnote 20: A merely disagreeable animal odour, without pungency, is here disregarded.]

[Footnote 21: 'Bulletin de l'Académie de Méd. Belgique,' ix, 304; 'Jahrb. f. prakt. Pharm,' xxiv, 313; &c.]

This method, according to Stas, answers well for all the ALKALOIDS which are soluble in ether; including--ACONITIA, ANILINE, ATROPIA, BRUCIA, CODEIA, COLCHICINA, CONIA, DELPHIA, EMETINA, HYOSCYAMINE, MORPHIA (?), NICOTIA, PETININE, PICOLINE, SOLANINE, STRYCHNIA, VERATRIA, &c. By means of it Stas found nicotia in the heart-blood of a poisoned dog. With such alkaloids as are, however, only very sparingly soluble in ether (as morphia for instance), the result must, necessarily, be doubtful. To detect these, as well as all the alkaloids which are insoluble in ether, it is, therefore, necessary, as directed by Otto, to add to the alkaline fluid left by the decantation of the ether, sufficient solution of soda to dissolve the morphia, &c. (if any has separated), and after the expulsion of the last traces of the ether by a gentle heat, to add a concentrated solution of hydrochlorate of ammonia, and to allow the mixture to repose for some time in the open air. When MORPHIA is present, it separates under the form of small crystals.[22] Or the alkaline liquor may be diluted with distilled water, and treated with charcoal, and this with alcohol, in the manner noticed under method 4 (_below_).

[Footnote 22: Otto's 'How to Detect Poisons.']

4. (Graham and Hoffmann--slightly modified.) 2 or 3 oz. of purified animal charcoal are digested in about 1/2 gal. of the (neutral or only slightly acid) aqueous fluid under examination, with frequent agitation, for 10 to 12 hours, or longer. The liquid is then filtered, and the charcoal left on the filter is washed twice with cold distilled water. The charcoal is then boiled for 1/2 an hour with about 1/2 a pint of rectified spirit of 80 or 90%; the ebullition being conducted in a flask having a very long tube, open at both ends, fitted air-tight through the cork, to prevent loss of the alcohol by evaporation. The spirit, which now contains the alkaloid (if any was present in the original liquor), is next filtered whilst hot, and the filtrate is submitted to distillation until the whole of the alcohol is removed. A small quantity (commonly a few drops) of solutions of potassa is then added to the residual aqueous liquor, followed by 1 to 2 fl. oz. of pure ether, after which the whole is well agitated for several minutes, and allowed to repose for a short time. Lastly, the supernatant ether is decanted, and allowed to evaporate spontaneously, when the residuum (if any) left in the capsule may be tested by reagents, as before.

This method was devised for the detection of STRYCHNIA and NUX VOMICA in malt-liquors; but it is equally applicable to the detection of ANY ALKALOID which is soluble in ether. The CHARCOAL TEST may also be employed to detect alkaloids which are insoluble in ether; but then the base must be sought in the aqueous residuum obtained by the evaporation of the alcohol.[23]

[Footnote 23: 'Journ. of the Chem. Soc.,' v, 173.]

The presence of the alkaloids and their salts, in clear solutions, may be thus determined:--

I. (Fresenius).--1. The solution is rendered very slightly alkaline with dilute solution of potassa or soda, added drop by drop:--

a. No precipitate is formed; total absence of the alkaloids.
(See 4, _below_.)

b. A precipitate is formed:--solution of potassa or soda is
added, drop by drop, until the liquid exhibits a strong
alkaline reaction:--

[Greek: a]. The precipitate redissolves; absence of Brucia,
Cinchonia, Narcotina, Quina, Strychnia, and Veratria; probable
presence of MORPHIA.

[Greek: b]. Precipitate does not redissolve, or not completely;
probable presence of one or more of the first six of the
above-named alkaloids:--the fluid is filtered from the
precipitate, mixed with either bicarbonate of soda or of
potassa, gently boiled nearly to dryness, and treated with
water. If it dissolves completely; absence of morphia; an
insoluble residue indicates MORPHIA.

2. The precipitate 1. _b._ [Greek: b]. is washed with cold distilled water, dissolved in a slight excess of dilute sulphuric acid, neutralised with a saturated solution of bicarbonate of soda, and allowed to repose a few hours:[24]--

[Footnote 24: Before setting the glass aside the liquor should be well mixed, and the glass stirrer vigorously rubbed against the sides of the vessel.]

_a_. No precipitate; absence of Cinchonia, Narcotina, and
Quina:--the solution is gently evaporated nearly to dryness,
and treated with cold water:--if it dissolves completely,
pass on to 4; if there is an insoluble residue, it may
contain Brucia, Strychnia, or Veratria. (See 3.)

_b._ A precipitate:--the filtered fluid is treated as directed
at 2 _a_.; the precipitate is washed with cold distilled
water, dissolved in a little hydrochloric acid, ammonia is
added in excess, and subsequently a sufficient quantity of
ether, agitation being had recourse to:--

[Greek: a]. The precipitate formed by the ammonia redissolves
completely in the ether, and the clear fluid separates
into two layers; absence of Cinchonia; probable presence
of QUINA or NARCOTINA.

[Greek: b]. The precipitate produced by the ammonia does not
redissolve in the ether, or not completely; probable presence of
CINCHONIA, and perhaps also of Quina or Narcotina. The
filtered liquid may be tested for these alkaloids as at
_a_.

3. The insoluble residuum after the evaporation of the solution 2. _a._, or of the filtrate 2. _b._, is now dried in a water bath, and digested with absolute alcohol:--

_a._ It dissolves completely; absence of strychnia; probable
presence of BRUCIA, QUINA (?), or VERATRIA:--the alcoholic
solution is evaporated to dryness, and, if quina has been
already detected, the residue is divided into two portions,
one of which is tested for Brucia, the other for Veratria.

_b._ It does not dissolve, or not completely; probable presence
of STRYCHNIA, and perhaps also of Brucia and Veratria:--the
filtered fluid is divided into two portions, and tested
separately as at _a_.

4. The original liquid 1. _a_. may contain Salicine, a proximate vegetable principle closely allied to the alkaloids:--a portion is boiled with hydrochloric acid for some time; the formation of a precipitate shows the presence of SALICIN. (See 2, _below_.)[25]

[Footnote 25: For further information on this subject, see the admirable 'System of Qual. Chem. Anal.,' by Dr C. R. Fresenius. Churchill.]

II. (Larocque and Thibierge.) Terchloride of gold is recommended, by these writers, as a more decisive test for the alkaloids than the 'double chloride of gold and sodium' commonly employed for this purpose. The following are the colours of the precipitates which it produces with the aqueous solution of their salts:--BRUCIA, milk-brown, passing into coffee-brown, and lastly chocolate-brown:--CINCHONIA, sulphur yellow:--MORPHIA, yellow, then bluish, and lastly violet; in this last state the gold is reduced, and the precipitate is insoluble in water, alcohol, the caustic alkalies, and sulphuric, nitric, and hydrochloric acid; it forms with aqua regia a solution which is precipitated by protosulphate of iron:--QUINA, buff-coloured:--STRYCHNIA, canary-yellow:--VERATRIA, pale greenish-yellow. All these precipitates, with the exception mentioned, are very soluble in alcohol, insoluble in ether, and only slightly soluble in water. Those with morphia and brucia are sufficiently marked to prevent these alkalies from being mistaken for each other; and those with brucia and strychnia are, in like manner, easily distinguishable.

III.--Mr Wanklyn discriminates the different alkaloids from the estimation of the ammonia they evolve. His process is as follows:--A small flask with a lateral tube, and connected with a Liebig's condenser, is charged with about 25 c. c. of an alkaline solution of permanganate potash made by dissolving 200 grammes of caustic potash and 8 grammes of crystallised permanganate of potash in 1 litre of water. A minute quantity of the alkaloid carefully and accurately weighed is now introduced, and the mixture slowly distilled. The most satisfactory results are obtained by treating from 1 to 5 milligrammes of the alkaloid in this way, but quantities so small as 1/10th of a milligram will in skilled hands give accurate results. The ammonia is formed in the distillate by Nesslerising it, as described under WATER ANALYSIS. For all practical purposes the poisonous alkaloids may be divided into four classes:

(a) Those which yield from 5 to 2 per cent. of ammonia.

(b) Those which yield from 2 to 3 per cent. of ammonia.

(c) Those which yield from 3 to 5 per cent. of ammonia.

(d) Those which yield a larger quantity than 5 per cent., _e.g._

I.

NH_{3}
per cent.

SOLANINE yields half its nitrogen as
Ammonia 0·98

II.

MORPHIA yields half its nitrogen as
Ammonia 2·98

CODEINE, ditto, ditto 2·87

PAPAVERINE, ditto, ditto 2·50

VERATRIA, ditto, ditto 2·87

III.

ATROPIA yields all its nitrogen as
Ammonia 5·73

NARCOTINE, ditto, ditto 4·11

STRYCHNIA yields half its nitrogen as
Ammonia 5·09

BRUCINE, ditto, ditto 4·32

ACONITE, ditto, ditto 3·50

CONEINE, ditto, ditto 4·60

IV.

NICOTINE yields half its nitrogen as
Ammonia 10·49

IV. Dr Guy, as well as others, have made researches, having for their object the determination of the exact temperature at which the poisonous alkaloids melt and sublime. A very minute speck of the substance is placed on a porcelain plate or copper disc, and a square or oval of microscope-covering glass is placed over it, supported by a thin ring of glass or any other convenient substance.

Heat is then applied to the plate or copper, and the temperature, as indicated by a thermometer at which the substance fuses or volatilises, is carefully noted.

CANTHARIDINE sublimes as a white Fahr. Cent.
vapour without change of form or colour. 212° 100°

Sublime. Melt.
/----------\ /----------\
Sublime, melt and Fahr. Cent. Fahr. Cent.
MORPHINE } yield carbonaceous { 330° 165° 340° 171°
STRYCHNINE} residue. { 345° 174° 430° 224°

Melt. Sublime.
/----------\ /----------\
Fahr. Cent. Fahr. Cent.
ACONITINE } { 140° 60° 400° 204°
ATROPINE } Melt, change { 150° 66° 280° 138°
VERATRINE } colour, sublime, { 200° 93° 360° 182°
BRUCINE } and { 240° 116° 400° 204°
DIGITALIN } deposit carbon. { 310° 154° 310° 154°
PICROTOXIN} { 320° 160° 320° 160°
SOLANINE } { 420° 215° 420° 216°

_Selmi's method of extracting poisonous alkaloids in forensic investigations._ The alcoholic extract of the viscera, acidified and filtered, is evaporated at 65° C., the residue taken up with water, filtered to separate fatty matters, and decoloured by means of basic acetate of lead, leaving the solution in contact with the air for 24 hours. It is then filtered, the lead precipitated by means of sulphuretted hydrogen, and the solution after concentration repeatedly extracted with ether. The ethereal solution is then saturated with dry carbonic anhydride, which generally causes a precipitate of minute drops adhering to the sides of the vessel, and containing some of the alkaloids. The ethereal solution is then poured into a clean vessel, mixed with about half its volume of water, and a current of carbonic anhydride passed for about twenty minutes, which may cause the precipitation of other alkaloids not precipitated by dry carbonic anhydride. Usually the whole of the alkaloids present in the ether are thrown down by these means, but if not, the solution is dehydrated by agitation with Barium oxide, and then a solution of tartaric acid in ether added to the clear liquid, taking great care not to employ excess of acid. This throws down any alkaloid that may remain. In order to extract any alkaloids that may still remain in the viscera, they are mixed with Barium hydrate and a little water, and then agitated with purified amylic alcohol; the alkaloids may subsequently be extracted from the alcohol by agitation with very dilute sulphuric acid.

A knowledge of the different solubilities of the alkaloids will be found an important auxiliary in their analysis. The following is a summary of the relative solubility of the most important of them. The figures denote the number of parts of the liquid required for their solution:--

_Absolute alcohol._--Strychnine insoluble; brucine soluble.

_Amylic alcohol._--Solanine (1061); digitalin sparingly soluble; morphine (133); strychnine (122); veratrine, brucine, atropine, aconitine, and picrotoxin, freely soluble.

_Benzol._--All the poisonous alkaloids, except solanine, are soluble in benzol.

_Chloroform._--Solanine (50,000); morphine (6550); strychnine (8); the rest freely soluble.

_Ether._--Solanine (9000); morphine (7725); strychnine (1400); aconitine (777); brucine (440); veratrine (108); atropine, picrotoxin,[26] and digitalin, very soluble.

[Footnote 26: Digitalin and picrotoxin, although not alkaloids, are inserted in the above list, because they have a general similarity in chemical properties to them; and for the convenience of the toxicologist.]

_Water_ (_cold_).--Strychnine (8333); veratrine (7860); morphine (4166); aconitine (1783); solanine (1750); brucine (900); atropine (414); picrotoxin (150); digitalin very soluble.

The principal Alkaloids and their Salts, in the state of powder, or with 'conia' and 'nicotia,' in the state of an oily looking liquid, may be thus distinguished:--

1. _a._ The powder is treated with nitric acid:--It is coloured red; probable presence of Brucia, Delphia, Morphia, or commercial Strychnia. If the reddened acid becomes violet on the addition of 'protochloride of tin,' it is BRUCIA; if it becomes black and carbonaceous, it is DELPHIA. If the powder is fusible without decomposition, and strongly decomposes iodic acid, it is MORPHIA; if it is not fusible without decomposition, and does not decompose iodic acid, it is STRYCHNIA.

_b._ If instead of a red, the powder strikes a green colour with nitric acid, it is SOLANIA; if it is insoluble in 'ether,' and not reddened by 'nitric acid,' it is EMETIA; if soluble in ether, not reddened by 'nitric acid,' but melts and volatilises when heated, it is ATROPIA; if it is thus affected by ether or nitric acid, but does not volatilise, it is VERATRIA. (See 2, _below_.)

2. _a._ The powder, or (with 'conia and nicotia') concentrated liquor, is treated with a drop or two of concentrated sulphuric acid:--A red colour is produced; probable presence of Brucia, Nicotina, Salicine, or Veratria. If the reddened mixture has at first a roseate hue, turning deep red on the addition of nitric acid, it is BRUCIA; if the original substance moistened with solution of potassa evolves the odour of tobacco, it contains NICOTINE; if the red colour produced by the acid is permanent and of an intense blood-hue, and the powder agglutinates into lumps like resin, it is SALICINE; if the colour is at first yellowish, changing to blood-red, and ultimately to crimson and violet, it is VERATRIA.

_b._ If instead of the substance being 'reddened' by strong sulphuric acid, no particular action ensues in the cold, it contains either Conia or Strychnia; if a small fragment of bichromate of potassa being now dropped in, produces a rich violet colour, it is STRYCHNIA; if the original matter on being heated, or treated with solution of potassa, evolves a penetrating, disagreeable odour, somewhat analogous to that from 'hemlock,' or to a mixture of those from tobacco and mice, it is CONIA.

"_Reactions with ceroso-ceric oxide._ This oxide exhibits characteristic colours with several alkaloids, especially with STRYCHNINE. When strong sulphuric acid is poured upon strychnine, and then a small quantity of ceroso-ceric oxide added, a fine blue colour is produced, similar to that which strychnine exhibits with potassium bichromate, but much more permanent. The blue colour gradually changes to cherry-red, and then remains unaltered for several days. This reaction is capable of detecting one part of strychnine in a million parts of liquid. BRUCINE similarly treated acquires an orange-colour, gradually changing to yellow; MORPHINE, olive-brown, finally brown; NARCOTINE, brown cherry red, finally wine-red; CODEINE, olive-green, finally brown; QUININE, pale-yellow; CINCHONINE and THEINE remain colourless; VERATRINE becomes reddish-brown; ATROPINE, dingy yellowish-brown; SOLANINE, yellow at first, finally brownish; EMETINE, brown; COLCHICINE, first green, then dirty brown; ANILINE, after a long time, acquires a blue colour extending from the edges inwards; CONINE becomes light-yellow. PIPERINE colours the sulphuric acid blood-red, and is turned dark-brown, almost black by the cerium oxide" (Sonnenschein).

"_Reactions with picric acid._ This acid is a very good precipitant for alkaloids, affording a very delicate test for many of them, and may perhaps also serve for separating them one from another. The precipitation takes place even in solutions containing a large excess of sulphuric acid, and is sometimes complete. _Precipitated_ are, BRUCINE, STRYCHNINE, VERATRINE, QUINIDINE, CINCHONINE, and most of the opium alkaloids; _not precipitated_, MORPHINE, ATROPINE (English), PSEUDO-MORPHINE, CAFFEINE, and all glucosides" (Hager).

The presence of one or more of the alkaloids being shown by any of the preceding methods, a portion of the original clear solution or powder, or of the precipitates or filtrates above referred to, must be treated with their characteristic tests, as given under the individual notices of these articles, so as to set at rest all doubt as to their identity. No single test must ever be relied on as a positive proof. The presence of Brucia, Morphia and Strychnia may be determined in substances which after being mixed with the salts of these alkaloids have undergone the acetous, vinous, or putrefactive fermentation, as shown by Orfila, MM. Larocque and Thibierge, and many other eminent chemists and toxicologists, and confirmed, in numerous cases, by our own experiments. Opium and morphia may thus be readily detected in beer, wine, soup, and milk. A paper by Professor DRAGENDORF in the 'American Chemist' for April, 1876, may be consulted with advantage.

_Concluding Remarks._ It is a singular fact that none of the organic bases found in plants have yet been formed artificially, although several analogous substances have been thus produced. Closely allied to the alkaloids there also exists an extensive series of neutral proximate principles, which differ from those substances chiefly in the absence of basic properties, and in most of them being destitute of nitrogen. They are usually bitter, and, like the alkaloids, generally represent the active properties of the plants in which they are found; whilst some of them possess considerable medicinal energy. Of this kind are asparagin, elaterin, gentianin, picrotoxin, salicin, &c. These two classes of bodies, though actually distinct, are frequently confounded. See ALKALI, ORGANIC BASES, POISONS, PROXIMATE PRINCIPLES, VEGETABLES, NOMENCLATURE, &c.; also the individual alkaloids under their respective heads.

=ALKALOIDS OF ACONITE=. The nature of the active principle of aconite root does not appear to have been satisfactorily determined. Messrs Groves, Wright, and Williams contend that the _Aconitum napellus_ yields an active crystalline alkaloid, which they distinguish as _Aconitine_, and to which they assign the formula C_{33}H_{43}NO_{12}; they add that additionally the root contains more or less of another active alkaloid, which they term _Pseudaconitine_, and which is represented by the formula C_{36}H_{49}NO_{11}; they also assert that the extract of the roots contains varying quantities of certain decomposition products resulting from the saponification of the above bases by the acids, which are produced by the breaking up of part of the aconitine. The name of these decomposition products is _Aconine_ and _Pseudaconine_. Of _Aconitum ferox_ they report that it yields a comparatively large quantity of _Pseudaconitine_ and a small quantity of _Aconitine_. They further affirm that the so-called aconitine of commerce is a mixture of true aconitine and pseudaconitine with variable quantities of their alteration products, aconine and pseudaconine, and of certain amorphous unnamed alkaloids.

Messrs Paul and Kingzett contest the accuracy of these deductions, and dispute the correctness of the formula given to aconitine. Dr Paul doubts whether the alkaloid to which the active properties of the root are ascribed has ever yet been obtained in an isolated condition. He thinks it probable that the substance obtained from aconite root was to a great extent a salt of an acid, like aconitic acid. For further information the reader is referred to the 'Pharmaceutical Year Book' for 1873, 1874, 1875, 1876, and 1877.

=AL'KANET.= _Syn._ ANCHU'SA, L.; ORCANETTE, Fr.; ORKANET, Ger.; OR'CHANET*, DYER'S AL'KANET, D. BU'GLOSS*. The _anchu'sa tincto''ria_ (Willd.; _lithosper'mum tincto''rium_--Linn.), a deciduous herbaceous plant, with a perennial, dark blood-red root. _Hab._ Asia Minor, Greece, Hungary, &c. It is also largely cultivated in the neighbourhood of Montpellier. The dried root (ALKANET ROOT; RADIX ANCHUSÆ, R. A. TINCTORIÆ) is chiefly imported from the Levant. It contains a beautiful blood-red colour, which it freely gives out to oils, fats, wax, spirits, essences, and similar substances, by simply infusing it in them, and is consequently much employed to colour these articles. Wax tinged with it, and applied on warm marble, stains it of a rich flesh-colour, which sinks deep into the stone, and possesses considerable durability. Its spirituous tincture also imparts a deep red to marble.

_Prop._, _&c._ The colouring matter of alkanet was regarded by Pelletier as a fatty acid (ANCHUSIC ACID); but it has since been shown to be a species of resin (ANCHUSINE, PSEUDO-ALKANNINE, P.-ALKANIUM). According to Dr John, good alkanet root contains 5-1/2 per cent. of this substance. Anchusine melts at 140° Fahr.; is scarcely soluble in water, to which it only imparts a dirty red colour, but is very soluble in alcohol, oils, and acetic acid. Alkalies turn it blue. It is found wholly in the root-bark. In selecting this article, the smaller roots should therefore be chosen, as they possess more bark than the larger ones, in proportion to their weight. Exposure to ammoniacal fumes, or even handling it much with the fingers, changes its red to a crimson or purplish hue.

_Uses_, _&c._ It is much employed by druggists and perfumers to colour oils, lip-salves, plasters, pomatums, &c.; by varnish-makers, to tinge their varnishes and lacquers; by statuaries to stain marble; by dairy-farmers, to colour cheese; by wine-merchants and bottlers (in the form of tincture), to stain beforehand the corks of their port-wine bottles, in order to imitate the effects of age, and as colouring and flavouring for factitious port wine; and by dyers, and others. A species of crimson rouge was formerly prepared from it (hence its name).

=ALLANTO'IC ACID.= See ALLANTOIN.

=ALLAN'TOIN.= C_{8}H_{6}O_{6}N_{4}. _Syn._ ALLANTO'IC ACID*, AMNIOT'IC A.[dagger] AM'NIC A.[dagger]; ALLANTOÏ'NA, L. A substance discovered by Vauquelin and Buniva in what they imagined to be the liquor amnii of the cow, and hence named by them amniotic acid. It was afterwards shown by Dzondi and Lassaigne to exist in the fluid of the allantoïs, and not of the amnios. It has since been produced artificially by Wöhler and Liebig.

_Prep._ 1. The allantoïc fluid of the f[oe]tal calf is evaporated to 1-4th or 1-5th of its volume, and then set aside for some time. The crystals thus obtained are purified by re-solution, digestion with animal charcoal, and re-crystallisation.

2. (Wöhler and Liebig.) Uric acid, 1 part; is dissolved in water, 20 parts; and freshly precipitated and well-washed binoxide of lead is added to the solution until the colour ceases to change; the liquid is next filtered while hot, evaporated until a pellicle forms on the surface, and then set aside to crystallise; the crystals being purified as before.

_Prop., &c._ Small, but very brilliant prismatic, transparent, colourless crystals; tasteless; neutral; soluble in 160 parts of cold water, and in much less at 212°; nitric acid converts it into ALLANTURIC ACID; oil of vitriol resolves it into ammonia, carbonic acid, and carbonic oxide; hot concentrated solutions of the caustic alkalies change it into ammonia and oxalic acid.

=ALLANTOX'ICUM.= [L.] _Syn._ ALLANTOX'ICUM, L. (prim., Gr.). The poison developed, during putrefaction, in sausages made of blood, liver, &c. "It often proves speedily fatal." (Kraus.)

=ALLGEMEINE FLUSSTINCTUR= (Sulzberger, Salzungen). For the relief of a number of diseases, among which are cholera and sea-sickness. Aloes, 1 part; spirit of wine, 2 parts. (Spau.)

=ALLIA'CEOUS= (-sh'us). _Syn._ ALLIA'CEUS, L.; ALLIACÉ, AILIACÉ, Fr.; KNOBLAUCHARTIG, &c., Ger. Garlick-like; an epithet applied to substances having the odour or properties of garlic or onions.

=Alliaceous Plants.= Chives, garlic, leeks, onions, rocambole, shallots, &c.

=ALLIGA'TION.= _Syn._ ALLIGA'TIO, L. In _commercial arithmetic_, a rule for ascertaining the price or value of mixtures, and for determining the proportions of the ingredients that must be taken to produce mixtures of any given price, value, or strength. The first is called ALLIGATION ME'DIAL; the second, ALLIGATION ALTERN'ATE. Its principles and applications are explained under MIXTURES (Arithmetic of).

=ALLOP'ATHY.= _Syn._ ALLOPA'THIA, L. (from [Greek: allos], _other_, _different_, and [Greek: pathos], _affection_ or _disease_, Gr.); ALLOPATHIE, Fr. In _medicine_, the method of curing disease by the use of remedies which tend to produce a condition of the system, either differing from, opposed to, or incompatible with the condition believed to be essential to the disease it is sought to cure. It is commonly employed to distinguish the ordinary system of medical practice from hom[oe]opathy (which see). Hence (an) ALLOP'ATHIST, and the corresponding adjective ALLOPATH'IC (_allopath'icus_, L.).

=ALLOT'ROPY.= _Syn._ ALLOT'ROPISM; ALLOTRO'PIA, ALLOTROPIS'MUS, L. Literally, a difference in character; another form of the same substance. In _chemistry_, a term invented, by Berzelius, to express the state or condition, or the change of character, assumed by certain substances at different temperatures, or under different treatment, whilst their nature and composition continue the same. It more particularly relates to colour, hardness, solubility, texture, &c. Boron, carbon, silicon, iron, sulphur, and phosphorus, afford striking examples of the changes here referred to.

=ALLOX'ANTIN.= C_{8}H_{4}N_{4}O_{7}.3H_{2}O. A crystallisable substance, first obtained by Dr Prout from uric acid.

_Prep._ 1. Uric acid, 1 part; is boiled in water, 32 parts; dilute nitric acid being added until solution is complete; the resulting liquid is evaporated to 2/3rds its volume, and then set aside for 10 or 12 hours; the crystals, which are deposited, are purified by re-solution and crystallisation.

2. Sulphuretted hydrogen gas is passed, in a full stream, through a moderately strong aqueous solution of alloxan, in the cold. The alloxantin, which is deposited as a crystalline mass, is purified by draining, cautious washing with cold water, re-solution in boiling water, and re-crystallisation. The impure mother-liquor from which crystals of alloxan have separated, if diluted with water, may be used for this purpose.

_Prop., &c._ Crystals, small colourless, transparent, four-sided, oblique rhombic prisms; scarcely soluble in cold water; solution reddens litmus; with baryta water it gives a characteristic violet-coloured precipitate, which disappears on heating; and with nitrate of silver a black precipitate of that metal; the crystals are reddened by ammoniacal vapours.

=ALLOY'.= _Syn._ ALLIAGE, Fr.; LEGIRUNG, VERMISCHUNG DURCH SCHMELZEN, Ger. In _coinage_, a compound of the precious metals with another, or others, of less value; also the least valuable metal, or metals, in such compounds. In _chemistry_ and _metallurgy_, combinations of the metals with each other usually obtained by fusion. When mercury is one of the component metals, the compound is termed an AMALGAM.