Cooley's Cyclopaedia of Practical Receipts Volume I Part 28

D - Whole numbers and decimals.

E - Nearest common numbers.

F - in quarter-grains.

G - in half-grains.

H - in grains.

-----------------------+-------+-------------------------------------------+ B --------------------^----------------------+ NAMES, &c C ------^-------- A D E F G H -----------------------+-------+------+--------+---------+--------+--------+ AMMONIA (pure, gaseous) 77273 7727 7-3/4 19-1/3 38-5/8 77-3/0 Carbonate of ammonia (neutral, anhydrous) 177273 17727 17-3/4 44-5/16 88-5/8 177-1/4 Carbonate of ammonia (neutral, crystallised) 19773 19773 19-3/4 49-7/16 98-7/8 197-3/4 Sesquicarbonate of ammonia (translucent) 26818 26818 26-13/16 67-1/10 134-1/10 268-1/5 Bicarbonate of ammonia (crystallised) 35909 35909 35-9/10 89-13/16 179-5/8 359-1/10 POTa.s.sA (anhydrous) 21364 21364 21-1/2 53-1/2 107 213-3/8 Hydrate of pota.s.sa 254546 25455 25-5/11 63-5/8 127-1/4 254-1/2 Carbonate of pota.s.sa (anhydrous) 31364 31364 31-3/8 78-1/2 157 313-1/2 Carbonate of pota.s.sa (granulated) 37727 37727 37-1/2 94-3/10 188-5/8 377-1/4 Carbonate of pota.s.sa (crystallised) 39545 39545 39-5/8 99 198 395-1/2 Bicarbonate of pota.s.sa (crystallised) 45454 45454 45-1/2 113-3/4 227-1/2 454-1/2 SODA (anhydrous) 14091 1409 14-1/10 35-1/4 70-1/2 141 Hydrate of soda 18182 18182 18-1/5 45-1/2 91 182 Carbonate of soda (anhydrous) 24091 24091 24-1/10 60-1/4 120-1/2 241 Carbonate of soda (crystallised) 65 65 65 162-1/2 325 650 Sesquicarbonate of soda (dry; theoretical) 29091 29091 29-1/10 72-1/2 145 290 Sesquicarbonate of soda (Ph. L., 1836) 37273 37273 37-1/4 93-1/4 186-1/2 373 Sesquicarbonate of soda (average commercial) 37954 37954 38 94-7/8 189-3/4 379-1/2 Bicarbonate of soda (crystallised) 38182 38182 38-1/5 95-1/2 191 382 LITHIA (pure, anhydrous) 6818 6818 6-13/16 17-1/20 34-1/10 68-1/5 BARYTA (pure, caustic) 34773 34773 34-4/5 86-7/8 173-7/8 347-3/4 LIME (pure, caustic) 12727 12727 12-3/4 31-3/4 63-5/8 127-1/4 MAGNESIA (pure, anhydrous) 90909 9091 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 quant.i.ty 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 a.s.say, being swelled by the disengagement of 'sulphuretted hydrogen' or sulphurous acid from these substances, a small quant.i.ty 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 pota.s.sa 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 pota.s.sa." (Fresenius.)

If the sodium or other carbonate under a.n.a.lysis 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.

[Ill.u.s.tration]

To obviate the difficulties, and to give greater precision and delicacy to volumetrical a.s.says, 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 quant.i.ty 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 gla.s.s 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 a.s.say, 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 quant.i.ty. 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 a.s.say of a sample of the unprepared alkali and of another which has been treated as above, indicates the quant.i.ty 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 pota.s.sa, is ascertained by any of the usual methods. The apparent quant.i.ty 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 quant.i.ty 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 quant.i.ty 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 gla.s.s 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.

1825, 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 quant.i.ty 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 : 5555

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 quant.i.ty only of test-acid as that referred to above is, of course, seldom made; but as any larger quant.i.ties 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 quant.i.ties of 10 lbs. each, and to preserve the liquid in stoppered green gla.s.s '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 POTa.s.sA (anhydrous).

{ 56 Hydrate of pota.s.sa (pure { caustic pota.s.sa).

{ 69 Carbonate of pota.s.sa { (anhydrous).

{ 83 " " (granulated, { commercial).

{ 87 " "

{ (crystallised).

{100 Bicarbonate of pota.s.sa { (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. 18485). } { (average commercial).

75 Tartaric acid } { 84 Bicarbonate of soda (crystals, (crystallised). } { or cryst. powder, 1000 Dilute sulphuric acid} { free from moisture).

(sp. gr. 1033). } { ============ } { Water--gr. measure. } { 15 LITHIA.

1000 Dilute sulphuric } { 24 Hydrate of lithia.

acid (sp. gr. 1032). } { 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; ALKALODES (_pl._, -IDES, or -IDae), L.; ALCALODE, 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 cla.s.s of bodies. They exist in nature nearly always in the form of salts, the acid being often, like themselves, peculiar to the plant, or cla.s.s 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, pota.s.sa, 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 pota.s.sa (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 pota.s.sa 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 pota.s.sa and ether, the former being in quant.i.ty 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, a.r.s.enic, antimony, or bis.m.u.th. 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 formulae; they may then be considered as hydrates of compound radicles a.n.a.logous 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 a.r.s.enic, 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 cla.s.sed 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 cla.s.s 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.