Chapter C: W. HEATON, F.I.C., F.C.S., Lecturer on Chemistry at the (3)

This method furnishes reliable results only with pure, or nearly pure solutions which do not contain much above 50% of glacial acid, or which have a sp. gr. not higher than 1·062. It is also more to be depended on for weak solutions than strong ones. By carefully diluting a strong acid with an equal weight, or twice or thrice its weight of water, and allowing the mixture to again acquire its normal temperature, the sp. gr. may be taken as a guide in all cases in which great accuracy is not required. When such dilution is made it only becomes necessary to multiply the indication furnished in the Tables by 2, 3, or 4, as the case may be. As, however, authorities are not agreed as to the precise sp. gr. of the monohydrate or glacial acid, and of its solutions, extreme accuracy must not be expected by this method.

TABLE I.--_Adapted to the Specific Gravities of common
vinegar_. By Messrs J. and P. TAYLOR.

per
sp. gr. cent.
1·0085 contains of anhydrous or real acetic acid 5
1·0170 " " 10
1·0257 " " 15
1·0320 " " 20
1·0470 " " 30
1·0580 " " 40

TABLE II.--_Exhibiting the quantity of_ ABSOLUTE _or_
GLACIAL ACETIC ACID (HC_{2}H_{3}O_{2}), _in acetic acid
of successive strengths_. By Mr COOLEY.

+---------+-------+---------+-------+---------+-------+---------+-------+
|Absolute | |Absolute | |Absolute | |Absolute | |
| Acetic |Sp. Gr.| Acetic |Sp. Gr.| Acetic |Sp. Gr.| Acetic |Sp. Gr.|
| Acid, | | Acid, | | Acid, | | Acid, | |
|per cent.| |per cent.| |per cent.| |per cent.| |
+---------+-------+---------+-------+---------+-------+---------+-------+
| _Pure | | | | | | | |
| acid_, | | 75 |1·0731 | 49 |1·0593 | 23 |1·0320 |
| or 100 |1·0630 | 74 |1·0732 | 48 |1·0582 | 22 |1·0311 |
| 99 |1·0648 | 73 |1·0728 | 47 |1·0568 | 21 |1·0292 |
| 98 |1·0663 | 72 |1·0721 | 46 |1·0557 | 20 |1·0275 |
| 97 |1·0677 | 71 |1·0718 | 45 |1·0553 | 19 |1·0264 |
| 96 |1·0685 | 70 |1·0713 | 44 |1·0544 | 18 |1·0253 |
| 95 |1·0696 | 69 |1·0711 | 43 |1·0535 | 17 |1·0241 |
| 94 |1·0704 | 68 |1·0708 | 42 |1·0525 | 16 |1·0229 |
| 93 |1·0708 | 67 |1·0702 | 41 |1·0518 | 15 |1·0218 |
| 92 |1·0715 | 66 |1·0701 | 40 |1·0513 | 14 |1·0200 |
| 91 |1·0721 | 65 |1·0693 | 39 |1·0502 | 13 |1·0173 |
| 90 |1·0726 | 64 |1·0692 | 38 |1·0492 | 12 |1·0172 |
| 89 |1·0729 | 63 |1·0685 | 37 |1·0482 | 11 |1·0161 |
| 88 |1·0730 | 62 |1·0679 | 36 |1·0473 | 10 |1·0150 |
| 87 |1·0731 | 61 |1·0675 | 35 |1·0460 | 09 |1·0131 |
| 86 |1·0732 | 60 |1·0672 | 34 |1·0449 | 08 |1·0121 |
| 85 |1·0733 | 59 |1·0665 | 33 |1·0439 | 07 |1·0102 |
| 84 |1·0734 | 58 |1·0662 | 32 |1·0425 | 06 |1·0085 |
| 83 |1·07343| 57 |1·0653 | 31 |1·0413 | 05 |1·0071 |
| 82 |1·0735 | 56 |1·0645 | 30 |1·0402 | 04 |1·0057 |
| 81 |1·0738 | 55 |1·0641 | 29 |1·0392 | 03 |1·0042 |
| 80 |1·0743 | 54 |1·0632 | 28 |1·0380 | 02 |1·0025 |
| 79 |1·0742 | 53 |1·0628 | 27 |1·0364 | 01 |1·0012 |
| 78 |1·0740 | 52 |1·0616 | 26 |1·0352 | _Pure |1·0000 |
| 77 |1·0739 | 51 |1·0610 | 25 |1·0341 | water._ | |
| 76 |1·0736 | 50 |1·0602 | 24 |1·0330 | | |
+---------+-------+---------+-------+---------+-------+---------+-------+

_Concluding remarks_. Before applying the above processes, account should be taken of any mineral acid which may be present in the sample, such being not unfrequently added to vinegar to impart artificial strength; and in those depending on the sp. gr., gum, gluten, &c., must also be allowed for. The methods depending on the saturating power of the acid will be found appropriate to acetic acid of all strengths, when unadulterated with the mineral acid. The method based on the sp. gr. is also very convenient, and is sufficiently accurate for distilled vinegars and for pure acids of moderate strength.

It is found that the decimal fraction of the sp. gr. of pure or nearly pure vinegar is doubled by its conversion into acetate of lime. Thus, 1·0085 in vinegar becomes 1·0170 when converted into a solution of acetate of lime. In malt vinegar, however, 0·005 may be deducted from the sp. gr. for mucilage and gluten. The quantity of foreign matter present in vinegar may therefore be approximatively ascertained, by deducting the decimal of the sp. gr. of the solution of acetate of lime from double that of the decimal part of the sp. gr. of the vinegar. Thus:--the sp. gr. of a sample of vinegar being 1·014, and after saturation with hydrate of calcium 1·023, the sp. gr. of the pure vinegar would be 1·009, and that due to foreign matter ·005. For--

·028 - ·023 = ·005

and--

1·014 - ·005 = 1·009

The reason why proof-vinegar is called, in commerce, No. 24, is that 1 fl. oz. of it requires exactly 24 gr. of pure anhydrous carbonate of soda to neutralise it. Weaker vinegars are represented in the same 'notation' by the Nos. 22, 20, 18, &c., according to their respective strengths estimated by their saturating power.

=ACETINE.= An essence for the removal of corns. Concentrated vinegar (1·04 sp. gr.) slightly tinged with fuchsine, 15 grms. (Hager.)

=ACETINE, HOCHSTETTER'S.= Prepared by J. C. F. Witte, Berlin. A remedy for corns, warts, and hard skin. Diluted vinegar, coloured with blue carmine, 16 grms. (Schälder.)

=ACETOLATS.= [Fr.] _Syn._ ESPRITS ACÉTIQUES. In _French pharmacy_, medicated vinegars obtained by distillation.

=ACETOLES.= [Fr.] In _French pharmacy_, medicated vinegars obtained by maceration.

=ACETOUS FERMENTATION.= See ACETIFICATION.

=ACETUM.= [L.] Vinegar.

=ACETYL.= _Syn._ ACETYLE. A name originally given to a hypothetical body, having the formula C_{2}H_{3}, and regarded by Berzelius as the radical of the acetates and their congeners. The acetyl of Gerhardt (C_{2}H_{3}O) is, however, according to that chemist, the true radical of the acetates. Williamson, in order to remove the confusion of terms occasioned by the application of the same name to compounds of different composition, proposed the title of othyl for the radical C_{2}H_{3}O.

=ACHAR.= See PICKLES.

=ACEIILE'INE= (-k[)i]l-). A peculiar bitter principle obtained from achillé a millefolium (Linn.), or yarrow.

=A'CHOR=, (-k[)o]r). [Gr.] See SCALD-HEAD.

=ACHROMAT'IC= ([)a]k-ro-). _Syn._ ACHROMATIQUE, Fr. In _optics_, devoid of colour; bodies that transmit light without decomposition, and consequently, without the formation of coloured rings or fringes; applied to compound lenses, prisms, &c., and to instruments fitted with them.

=ACRO'MATISM.= _Syn._ ACHROMATISME, Fr. In _optics_, the state of being achromatic; the absence of coloured fringes in the images of objects seen through a lens or prism.

Light is not homogeneous, but decomposable by refraction, absorption, or reflection, into coloured rays of unequal refrangibility. A ray of white light, in passing through a glass prism, is entirely separated into the coloured rays forming the 'prismatic spectrum,' and when it passes through a lens, an analogous resolution into coloured rays still occurs, though not so readily observed, and that to an extent often incompatible with distinct vision. Now, if a convex lens be regarded as a number of prisms united by their bases round a common centre, and a concave lens, as a similar number of prisms with their apices in contact, the action of lenticular and prismatic glasses on light will be reduced to a common principle. A beam of light thrown on a simple converging lens not only suffers refraction at the spherical surface (SPHERICAL ABERRATION), but the different coloured rays of which it is composed, from the causes mentioned, being unequally bent or refracted, diverge from their original course (CHROMATIC ABERRATION), forming as many foci on the axis of the lens as there are colours, and fall separately, instead of together, on the eye or object which receives them. Hence arise the coloured fringes or halos that surround objects viewed through ordinary glasses, and which form the great impediments to the construction of perfect lenses. This effect, like the refractive power and focal distance, varies in degree in different diaphanous substances.

The correction of the chromatic aberration of lenses is commonly effected by combining two, or more, made of materials possessing different 'dispersive' powers. Thus, the spectrum formed by flint glass is longer than that formed by crown glass, for the same deviation. When the two are combined, so as to form a compound lens, the one tends to correct the 'dispersion' of the other. On this principle ACHROMATIC GLASSES are generally formed in this country. A convex lens of crown glass is combined with a weaker concave lens of flint glass, the latter counteracting the dispersion of the former, without materially interfering with its refractive power. The resulting combination is not absolutely achromatic, but is sufficiently so for all ordinary purposes. According to Dr Blair, a compound lens perfectly achromatic for the intermediate, as well as for the extreme rays, may be made by confining certain fluids, as hydrochloric acid, between two lenses of crown glass. In order to produce nearly perfect achromatism in the object-glasses of telescopes, microscopes, cameras, &c., a concave lens of flint glass is commonly placed between two convex lenses of crown or plate glass, the adjacent surfaces being cemented with the purest Canada balsam, to prevent the loss of light by reflection from so many surfaces.

_Obs._ The production of perfect achromatism in lenses is a subject not less fraught with difficulty than with practical importance to the astronomer, the mariner, the microscopist, and the photographer; and it has hence engaged the attention of the leading mathematicians and artists of Europe up to the present time. All the larger object-glasses lately manufactured are said to consist of only two lenses; the resulting achromatism proving sufficiently exact for all useful purposes. Those of recent production have come chiefly from the workshops of Dollond, of London, and the opticians of Bavaria and Switzerland. The achromatism of prisms depends upon the same principles, and it is effected in the same way as that of lenses.

=ACIC'ULAR.= Needle-shaped; slender or sharp pointed; spicular; in _botany_, applied to leaves, and in _chemistry_, to crystals. The last are also sometimes termed ACIC'ULÆ.

=ACID=, _Syn._ ACIDUM, L.; ACIDE, Fr.; ACIDO, Ital.; SÄURE, G. In familiar language, any substance possessing a sour taste. In _chemistry_, substances are said to be acid, or to have an acid reaction, when they are capable of turning blue litmus red. In _chemistry_, also, the term acid is applied to a very large class of compounds containing hydrogen (hydrogen salts), and in which one or more atoms of that element may be replaced by an equivalent quantity of a metal or other basic radical; _e.g._--

1. The one atom of hydrogen in hydrochloric acid (HCl) may be replaced by sodium, producing the salt sodium chloride (NaCl).

2. The one atom of hydrogen in nitric acid (HNO_{3}) may be replaced by silver, producing the salt silver nitrate (AgNO_{3}).

3. One atom of hydrogen in acetic acid (HC_{2}H_{3}O_{2})[6] may be replaced by the basic radical ammonium (NH_{4}), producing the salt ammonium acetate (NH_{4}C_{2}H_{3}O_{2}).

[Footnote 6: Symbols indicating the number of atoms of replaceable hydrogen occupy the foremost position in the formulæ of acids, as shown in the text.]

Acids which, like those mentioned in the foregoing examples, contain one atom of replaceable hydrogen are called monobasic; those which contain two such atoms (_e.g._ sulphuric acid, H_{2}SO_{4}; tartaric acid, H_{2}C_{4}H_{4}O_{6}),[7] dibasic; those which contain three such atoms (_e.g._ phosphoric acid, H_{3}PO_{4}; citric acid, H_{3}C_{6}H_{5}O_{7}),[7] tribasic; and so on with acids of higher basicity. Acids of greater basicity than unity are frequently termed polybasic.

[Footnote 7: See footnote, p. 26.]

Besides containing replaceable or basic hydrogen, acids are further characterised by the property of combining with alkaloids to form salts; _e.g._--

Sulphuric Acid. Quinia.
H_{2}SO_{4} + 2C_{24}H_{24}N_{2}O_{2} =

Quinia Sulphate.
(C_{20}H_{24}N_{2}O_{2})_{2} . H_{2}SO_{4}

Acetic Acid. Morphia.
HC_{2}H_{3}O_{2} + C_{17}H_{19}NO_{3} =

Morphia Acetate.
C_{17}H_{19}NO_{3} . HC_{2}H_{3}O_{2}

=Dibasic Acids.= See ACID.

=Fatty Acids.= Acids separable from fats or oils; _e.g._ stearic acid, oleic acid, butyric acid, &c.

=Inorganic Acids.= Same as MINERAL ACIDS (which _see_).

=Mineral Acids.= Acids chiefly or wholly derived from the mineral kingdom. In _medicine_, sulphuric, hydrochloric, and nitric acids, are commonly so called.

=Monobasic Acids.= See ACID.

=Organic Acids.= Acids formed by, or derived from organic substances; _e.g._ acetic acid, tartaric acid, uric acid, &c.

=Polybasic Acids.= See ACID.

=Pyro-acids.= Acids resulting from the decomposition by heat of other acids, _e.g._ gallic acid, when heated, yields pyro-gallic acid.

=Tribasic Acids.= See ACID.

=ACIDIFICA'TION.= [Eng., Fr.] _Syn._ ACIDIFICA'TIO, L. In _chemistry_, the act, process, or state of acidifying, or of making, becoming, or impregnated with acid.

=ACIDIM'ETER.= _Syn._ ACIDOM'ETER; ACIDIME'TRUM, &c., L.; ACIDIMÈTRE, Fr. An instrument or apparatus employed in acidimetry.

The ordinary acidimeters of the chemist are small tubes, constructed to hold exactly 1000 grains of distilled water, at 60° Fahr., within the limits of their scale, which is accurately graduated into 100 divisions. They are used to contain the alkaline solutions (TEST-LIQUORS, NORMAL or STANDARD SOLUTIONS) employed in the following processes.

Beaumé's Acidimeter, and others of the same class, are HYDROMETERS, and are described under that 'head.'

=ACIDIM'ETRY.= _Syn._ ACIDOM'ETRY; ACIDIME'TRIA, &c., L.; ACIDIMÉTRIE, Fr. The estimation of the strength or quantity of acid, in a free state, contained in any liquid. It is the reverse of 'alkalimetry.' Acidimetrical assays are understood to refer to the relative strengths of the same acids (_i. e._, the quantity of real acid of the same kind contained in the solutions examined), and not to the comparative strengths of acids of different composition or names.

_Acidimetrical processes._ These are founded chiefly on the capacity of the acids to saturate the bases; and, in some of the liquid acids, on the specific gravity.

_a._ VOLUMETRICALLY:--

1. The sample of the acid to be examined (100 gr., or any convenient aliquot part thereof) is placed in a suitable glass vessel, and if it be one of the stronger acids, diluted with six or eight times its weight of water, or if solid (as oxalic, or citric acid), dissolved in a like quantity. This liquid is then exactly neutralised with an alkali.

This point is usually determined, by the addition of a small quantity of litmus solution, which turns just blue when the solution is neutralised, but when a carbonate is used for the alkaline solution, the acid must be boiled a short time after each addition to expel the carbonic acid. The quantity of the alkaline solution consumed for this purpose represents an equivalent quantity of acid, and thus gives us the acid content of the sample under examination. The common practice is to dissolve one equivalent of the alkaline test in grains or grammes in water, and to make up the solution to exactly 1000 parts by measure (_i. e._, 1000 'water-grains' or grammes), so as to accurately fill the 100 divisions of an acidimeter; when the quantity, in grains or grammes, of the sample tested, bears the same proportion to the equivalent number of the acid under examination, that the number of acidimeter divisions of the test-liquor consumed bear to the per-centage of acid sought. Thus:--suppose 50 gr. of a sample of sulphuric acid take 25 acidimeter divisions (300 parts or water-grains measure) of the test-liquid to neutralise it, what is its content of real acid?

The equivalent of sulphuric acid is 49 (half its atomic weight); so, by the rule of proportion,

50 : 49 :: 25 : 24-1/2

It therefore contains 24-1/2 parts of real sulphuric acid, in 50.

If the 1000 parts or grain-measures, instead of the number of the acidimeter divisions, be taken for the calculation, it will, of course, be necessary to point off the first right-hand figure of the result as a decimal. Thus; repeating the above example--

50 : 49 :: 250 : 24·5

Or, since the equivalent of the test-liquid is 100, it will bear the same proportion to the equiv. of the acid examined as the number of the acidimeter divisions of the test-liquid consumed in neutralising 100 gr., do to the per-centage sought. Thus:--50 gr. of hydrochloric acid take 45 acidimeter divisions to effect neutralisation, what is its real strength?--The equiv. of hydrochloric acid is 36·5: therefore--

100 : 36·5 :: 45 : 16·425%

and, since only 50 gr. (instead of 100 gr.) were examined--

16·425 × 2 = 32·85%

Some operators prefer employing 100 gr. instead of the equivalent weights of the given tests in making their test-solutions, in which case each gr. or 1000th part represents 1/10th, and each acidimeter degree 1 gr. of the alkali or carbonate employed; when a similar proportion will obtain to that first above given.

In technical analysis it is more convenient if the number of acidimeter divisions of the 'test-liquid' consumed express the per-centage strength of the acid, without further calculation. For this purpose the number of grains of the acid taken for the assay should correspond to the equivalent number of such acid (see _Table_ I, below); or to some convenient aliquot part of it, as the 1/2, 1/4, 1/5, or 1/10th; the per-centage answer, in the last case, being doubled, quadrupled, &c., according to the aliquot part taken. The reason of this is obvious.

For the test-solutions, ammonia, and the dry and crystallised carbonates and bicarbonates of potash and soda, are used, and are made by dissolving in water their constituents except ammonia, of which 1000 grains, or one litre, of solution of specific gravity 0·992 contains exactly one equivalent.

53 grains (or grammes) of pure anhydrous carbonate of soda, prepared by gradually heating to redness the crystallised salt, constitute one equivalent (half the atomic weight), and 69 grains (or grammes) of pure dry carbonate of potash. Of the crystallised salt 143 grains of carbonate of soda will be required, and 84 grains (grammes) of the crystallised bicarbonate of soda, and 100 of the crystallised bicarbonate of potash. Occasionally solutions containing in one thousand parts, 50 of pure carbonate of lime or chalk, or 28 of pure caustic lime, are used.

Besides these, a process known as Kiefer's is practised, and an ammoniacal solution of oxide of copper is employed as the 'test-liquor,' and the 'point of neutralisation' is known by the turbidity observed as soon as the free acid present is completely saturated.

The normal solution or test-liquor is prepared by adding to an aqueous solution of sulphate of copper, pure ammonia water, until the precipitate, which at first forms, is just redissolved, carefully avoiding excess. Or better, by adding a rather strong solution of sulphate of copper, to a quantity of a rather strong solution of ammonia containing exactly 17 gr., or one equiv. of pure ammonia, as long as the precipitate which forms is redissolved on agitation; the resulting liquid being afterwards diluted with pure distilled water, until it accurately measures 1000 water-grains, or fills 100 divisions of an acidimeter, at 60° Fahr. In either case, the strength of the resulting 'test-solution' must be carefully determined by means of standard sulphuric acid, and adjusted, if necessary.

This method answers well with all the stronger acids (excepting oxalic acid), even when dilute; and it has the advantage of not being affected by the presence of a neutral metallic salt with an acid reaction, as sulphate of copper, or of zinc.

Besides this process a solution of lime in sugar may be used, as proposed by M. Peligot, and made as follows:--

Pure caustic lime is carefully slaked by sprinkling with water, and 50 grains (or grammes), made up by water to a milky solution, and 100 grains of pure sugar candy dissolved in 1000 grains of water, are added, and the whole well shaken. It is allowed to settle in a closed bottle, and the clear solution poured off and diluted, until 1000 grains neutralise exactly 100 grains of pure hydrochloric acid of sp. gr. 1·1812. Of course it only answers with acids whose calcium salts are readily soluble in water.

_b._ GRAVERMETRICALLY:--

The test-liquors or standard solutions of the above methods are made up so as to _weigh_ exactly 1000 grains, instead of to 'measure' 100 acidimeter divisions. Every grain of the test-liquor thus represents 1/10th gr. of alkali; and every 10 gr., 1 gr. of alkali; or respectively, 1/10th per cent. and 1 per cent. The vessel used for containing the solutions is carefully weighed whilst empty, and 1000 gr. being placed in the opposite scale, the test-solution, containing exactly one equivalent of base, is poured in, and the whole made up with distilled water (if necessary) so as to restore the balance to an equilibrium. After the process of neutralisation, the acidimeter, with its contents, is again placed in the scales; its previous weight still remaining there. The number of grains required to restore the equilibrium of the balance (_i.e._, the loss of weight), gives the exact weight of the test-liquor consumed. In all other respects the process is the same as in the 'volumetrical method' already described.

Another method for estimating the strength of the sample of acid is by weighing the amount of carbonic acid expelled during saturation. (Method of Fresenius and Will.) This depends on the weight of gaseous carbonic acid which a given weight of the acid-sample under examination is capable of expelling from pure bicarbonate of soda (or of potash), which is estimated by the loss of weight in the acidimeter, or apparatus, after the gas, rendered perfectly dry by passing through sulphuric acid, has escaped into the air.

TABLE I.--_Weights of the respective acids equivalent
to the given weight of the principal bases, hydrogen
being taken as unity._

{51 Acetic acid (anhydrous).
{60 " " (crystallised or glacial).
{99 Arsenious acid (dry).
{35 Boracic acid (anhydrous).
17 gr. of pure ammonia.[8] } {62 " " (crystallised).
31 " anhydrous soda.[9] } {22 Carbonic acid (dry).
40 " hydrate of soda.[9] } {67 Citric acid (crystallised).
53 " dry carbonate of soda.[10] } {85 Gallic acid (dried at 212°).
143 " crystallised carbonate of } {94 " " (crystallised).
soda.[11] } {127-1/2 Hydriodic acid (dry or gaseous).
84 " crystallised bicarbonate } {27 Hydrocyanic acid (anhydrous).
of soda. } {36-1/2 Hydrochloric acid (dry or gaseous).
47 " anhydrous potassa.[9] } {109 " " (liquid, sp. gr. 1·162).
56 " hydrate of potassa.[9] } are {166-1/2 Iodic acid.
69 " dry carbonate of potassa.[10]} exactly {54 Nitric acid (anhydrous).
100 " crystallised bicarbonate } neutralised {63 " " (liquid, _monohydrated_, sp. gr.
of potassa. } by { 1·517 to 1·521).
50 " {pure chalk. } {67-1/2 " " (liquid, _sesquihydrated_, sp. gr.
{pure marble. } { 1·5033 to 1·504).
28 " pure caustic lime. } {72 " " (liquid, _binhydrated_, sp. gr.
37 " hydrate of lime (fresh). } { 1·486).
44 " dry carbonic acid (when } {90 " " (liquid, sp. gr 1·42).
the bicarbonate of } {36 Oxalic acid (anhydrous).
potassa or soda is } {63 " " (crystallised).
used for testing in } {72 Phosphoric acid (anhydrous).
the process of Fresenius } {81 " " (glacial).
and Will). } {50 Succinic acid (dry or anhydrous crystals).
22 " dry carbonic acid (when } {59 " " (ordinary crystals).
a dry carbonate is } {40 Sulphuric acid (anhydrous).
used). } {49 " " (liquid, _monohydrated_, sp.
{ gr. 1·8485).
{75 Tartaric acid (crystallised).
{212 Tannic acid (carefully dried).

[Footnote 8: 1000 water-grains measure of pure liquor of ammonia, sp. gr. 0·992, contains exactly 17 gr., or 1 equiv. of pure gaseous ammonia. A standard liquor of this strength may be most conveniently prepared by cautious dilution of a stronger solution, until a hydrostatic bead, corresponding to the sp. gr., floats indifferently in the middle of the new solution, at 60° Fahr. By keeping two hydrostatic beads in the solution--the one made barely to float, and the other barely to sink--we shall always be able to detect any change of strength or temperature which it may suffer; since the "loss of a single hundredth part of a grain of ammonia per cent., or the difference of a single degree of heat, will cause the beads to" vary their positions. To preserve its integrity it must be kept in a well-stoppered bottle. (See below.)]

[Footnote 9: These substances, as well as 'test-solutions' containing them, must be perfectly free from carbonic acid, and must be carefully preserved to prevent the absorption of carbonic acid from the atmosphere. Mohr states that a dilute solution of either of them is best preserved in a flask or bottle well closed with a cork fitted with a small bulb tube (resembling a chloride of calcium tube), filled with a finely triturated mixture of sulphate of soda and caustic lime, and bearing a very thin open tube in the exit aperture. Fresenius, and most other foreign chemists, prefer 'test-solutions' of pure soda. With test-solutions containing caustic alkalies, exact neutralisation of an acid is not only more easily effected, but more readily perceived, particularly when either solution is tinted with litmus.]

[Footnote 10: Prepared by gradually heating the pure crystallised carbonate to redness. From being uniform in composition, and easily procured or prepared, they are much employed; preference being usually given to the soda-salt.]

[Footnote 11: The crystals must be free from attached water, but not the least effloresced.]

_Oper._ A determined amount of the acid under examination is accurately weighed into the flask _A_ (see _engr._); and if it be a concentrated acid, or a solid, it is mixed with or dissolved in 6 or 8 times its weight of water. The little glass tube (_e_) is then nearly filled to the brim with pure bicarbonate of soda, in powder, and a fine silken thread is tied round the neck of the tube, by means of which it can be lowered down into the flask (_A_), so as to remain perpendicularly suspended when the cork is placed in the latter; the cord being held between the cork and the mouth of the flask. The flask (_B_) is next about half filled with oil of vitriol, and the tubes being arranged in their places, as represented in the _engr._; and time having been allowed for the mixture of acid and water to cool completely, after the increase of heat caused by mixing, the whole apparatus is very accurately weighed. The cork in the flask (_A_) is then slightly loosened, so as to allow the little tube containing the bicarbonate of soda to fall into the acid, and is again instantly fixed AIR-TIGHT in its place. The evolution of carbonic acid now commences, and continues until the acid in the flask (_A_) is neutralised. When this takes place, which is easily seen by no bubbles being emitted on shaking the apparatus, the flask (_A_) is put into hot water (120° to 130° Fahr.), and kept there, with occasional agitation, until the renewed evolution of gas has completely ceased. The little wax stopper is then taken off the tube (_a_), the apparatus taken out of the hot water, wiped dry, and suction applied, by means of a perforated cork, or a small india-rubber tube, and the mouth, to the end of the tube (_d_), until the sucked air no longer tastes of carbonic acid. The whole is then allowed to become quite cold, when it is replaced in the balance (the other scale still containing the original weights), and weights added to restore the equilibrium.

(_A_) A wide-mouthed flask, capable of holding 2-1/2 to 8 oz.,
containing sample for trial (_f_).
(_B_) Ditto, capable of holding 1-1/2 to 2 oz., partly filled with
oil of vitriol (_g_).
(_a_, _c_, _d_) Tubes fitting air-tight in the flasks by means of
the corks (_i_) and (_j_).
(_b_) Piece of wax fitting air-tight on the end of _a_.
(_e_) Small tube capable of holding about 1 drachm of powdered
bicarbonate of soda or potash.
(_h_) Open end of the tube (_d_).
(_k_) Silk cord fastened to the tube (_e_).]

The loss of weight represents the exact quantity of dry carbonic anhydride, or anhydrous carbonic acid gas, that has been expelled from the bicarbonate of soda, by the action of the acid in the sample examined.

The quantity of real acid it contained is then deduced by the following calculation:--One equivalent of gaseous carbonic anhydride, or anhydrous carbonic acid (= 44) bears the same proportion to one equivalent of the acid in question, as the amount of the carbonic anhydride expelled does to the amount of the acid sought. Thus, suppose a dilute sulphuric acid expels 3 gr. of carbonic anhydride, the arrangement is--

44 : 49 :: 3 : 3·349

Consequently the sample operated on contained 3·5 (nearly) grains of true sulphuric acid.

Instead of the above calculation, we may multiply the weights of the respective acids required to expel 1 gr. of carbonic acid (as exhibited in the following table) by the number of gr. of dry carbonic acid evolved during the above operation. The product represents the per-centage strength, when 100 gr. of the acid have been examined. When only 50, 25, 20, or 10 gr. have been tested, this product must, of course, be doubled, quadrupled, &c., as the case may be.

TABLE II.

Multipliers.
Acetic acid (anhydrous) 1·159
" " (hydrated or glacial) 1·364
Citric acid (crystallised) 1·523
Hydrochloric acid (dry or gaseous) ·829
" " (sp. gr. 1·16) 2·478
Nitric acid (anhydrous) 1·227
" " (sp. gr. 1·5) 1·523
" " (sp. gr. 1·42) 2·045
Oxalic acid (crystallised) 1·432
Sulphuric acid (anhydrous) ·909
" " (sp. gr. 1·8485) 1·114
Tartaric acid (anhydrous) 1·500
" " (crystallised) 1·705

Even this easy calculation may be avoided, in technical analysis, by simply taking for the assay such a weight of the respective acids as is capable of disengaging exactly 10 gr. of dry carbonic acid from the bicarbonate. In this case, the loss of weight in grains, from the operation, multiplied by 10, at once indicates the exact per-centage strength sought. The proper weight of any acid to be taken to give per-centage results is found by simply dividing ten times the equiv. of that acid by 44. For, taking sulphuric acid as an example,

as-- 44: 49 :: 10 : 11·1318

or 11·13 nearly.

On this principle are obtained the weights to be taken, as given in--

TABLE III.

Grains.
Acetic acid (anhydrous) 11·59
" " (hydrated or glacial) 13·64
Citric acid (crystallised) 15·23
Hydrochloric acid (dry or gaseous) 8·29
" " (sp. gr. 1·16) 24·78
Nitric acid (anhydrous) 12·27
" " (sp. gr. 1·5) 15·23
" " (sp. gr. 1·42) 20·45
Oxalic acid (crystallised) 14·32
Sulphuric acid (anhydrous) 9·09
" " (sp. gr. 1·845) 11·14
Tartaric acid (anhydrous) 15·00
" " (crystallised) 17·05

2. A convenient modification of the preceding method of acidimetry consists in using the common apparatus figured in the margin and employing fused chloride of calcium to dry the evolved carbonic acid gas, instead of concentrated sulphuric acid. The mode of conducting the process and obtaining the results is precisely the same as in that last explained, and need not, therefore, be repeated. In this case, however, suction must be applied to the small tube (_g_), instead of (_d_) in the accompanying engraving.

_Obs._ These methods, though apparently complicated, are not difficult to perform, when once well understood. The application of heat after the completion of the operation is indispensable, as, if it were neglected, from 0·3 to 0·4 of a gr. of carbonic acid would be retained in the liquid. The bicarbonate of soda must be pure, and perfectly free from any neutral carbonate or sesquicarbonate of soda. To ensure this, the bicarbonate of commerce is reduced to a uniform powder, put into a glass jar, and covered with its own weight of cold distilled or rain water, and allowed to stand for twenty-four hours, with frequent stirring. It is then placed upon a funnel, the tube of which is stopped with loose cotton, so as to allow the lye to drain off. It is next washed several times with small quantities of cold distilled or rain water, and after being dried by pressure between some sheets of blotting-paper, without the aid of heat, is kept for use in a well-closed glass bottle. Before use, it may be tested to ascertain its purity. If pure, it neither reddens turmeric paper, nor gives a brick-red precipitate with a solution of bichloride of mercury. Pure bicarbonate of potassa may be used instead of bicarbonate of soda; but in either case it is always proper to use an excess, so as to leave some undecomposed carbonate after the operation has ended. The presence of a little sodium chloride or sulphate in the bicarbonate will not interfere in the least, but the absence of every trace of neutral carbonate is a _sine quâ non_.

(_a_) Wide-mouthed flask, containing the sample for examination,
hermetically stopped by the cork (_e_) and supporting the
tubes (_b_) and (_c_).
(_b_) Bulbous tube, containing fragments of fused chloride of
calcium, terminating in a capillary tube (_g_).
(_c_) Bent tube, reaching nearly to the bottom of the flask (_a_).
(_d_) Small tube containing bicarbonate of soda.
(_e_) Cork fitting bottle (_a_), and the tubes (_b_) and (_c_),
hermetically.
(_f_) Silken thread, suspending the small tube (_d_).]

The two above methods of estimating the amount of acid are only superior to the generally used methods first described, when the presence of colouring matter interferes with the reaction of the litmus used to show the point of neutralisation.

_Observations._ When great accuracy is required in conducting the neutralisation of the solution in estimating volumetrically with litmus as an indicator, it is proper to prepare and keep standard solutions of sulphuric acid and oxalic acid, with which occasionally to try the alkaline test-liquor. The only difficulty in the process is to avoid over-saturation of the acid-sample. Great care must be taken not to exceed the precise point of neutralisation of the acid. After adding each portion of the test-liquor, the solution should be well stirred up, and as soon as the effervescence becomes languid the greatest caution must be observed in adding more. The proper point is arrived at when the liquor ceases to redden litmus, and does not alter the colour of turmeric paper; if it turns the latter brown, too much of the test-liquid has been added, and the operation becomes useless. Towards the end of the experiment, when great precision is required, a gentle heat may be applied, in order to expel the free carbonic acid in the liquor; but otherwise this is unnecessary. The peculiar soapy odour gradually acquired by the liquor as it nears saturation will materially assist the operator when testing vinegars, and some of the other vegetable acids. A good method is to tint either the acid-sample or the test-liquid with a few drops of litmus, as noticed under ACETIMETRY; when the reddish shade will gradually deepen into 'purple,' or the purple into 'red,' as the point of saturation is approached; and the blue colour will be perfectly restored as soon as this point is reached. Dr Ure recommends keeping the ammonia-test ready tinged with litmus, and the same applies to other test-liquors.

In commerce, the strength of acids is frequently reckoned with reference to a standard, termed 100 acidimetric degrees. This is taken from the circumstance that 91 gr. of commercial oil of vitriol, of a sp. gr. of 1·845, exactly saturate 100 gr. of dried carbonate of soda. An acid requiring only 35, 50, or any other number of grains of the carbonate to saturate it, is in like manner termed of so many degrees strong; the number of grains representing in each case an equal number of degrees. This method originated with the French chemists, and though only conventional, and principally confined to commercial purposes, is especially adapted to practical men but little conversant with chemistry, yet very ready in retaining or calculating anything on the centesimal scale, from its similarity to monetary language and reckoning.

=ACID'ITY.= _Syn._ ACID'ITAS, L.; ACIDITÉ, Fr.; SÄURE, Ger. In _chemistry_, the state of being acid. In _physiology_, &c., the impression given to the organs of taste by tart or acid substances. Sourness. See FERMENTATION, MALT-LIQUORS, WINES, &c.

=Gas'tric Acidity.= Acidity of the stomach; a common and well-known symptom of weak or disordered digestion.

_Treat., &c._ Small doses of absorbents or antacids, three or four times daily, to which some tonic bitter, as calumba, cascarilla, chamomile, gentian, or orange-peel, may be added. Stomachic stimulants, as capsicum, ginger, mustard, or wine, &c., taken with, or after, meals, are also useful. The diet should be light and nutritious; and acescent vegetables, over-ripe fruit, and weak new beer or other liquors avoided as much as possible. The bowels should be kept regular, but not open, by the occasional use of mild aperients, as rhubarb, aloes, castor oil, senna, or mercurial pill, or compounds containing them. Excessive looseness or diarrh[oe]a may be checked by a few doses of carbonate of soda, chalk-mixture, or astringents.

In INFANCY this affection is usually accompanied by restlessness, continual crying, drawing up of the legs forcibly towards the body, hiccups, vomiting, diarrh[oe]a, sour eructations, griping pains, green stools, and debility; often followed, when the irritation is considerable, by convulsions. The treatment consists in relieving the bowels of all offending matter by a few doses of rhubarb-and-magnesia. The looseness or diarrh[oe]a may be checked by a few small doses of carbonate of soda or chalk mixture; or better, in an infant which is fed by lime-water (1 or 2 fl. oz.) mixed with as much milk. Two or three drops of caraway, cinnamon, dill, or peppermint water, on sugar (not with the food) will tend to promote the expulsion, and prevent the undue generation of gases. The flatulence usually disappears with the acidity. The occasional administration of 1 to 3 gr. of quicksilver-with-chalk ('grey powder'), will frequently remove the complaint, and prevent its recurrence, when all other means fail. The diet of both nurse and infant should be carefully regulated.

See ANTACIDS, DYSPEPSIA, &c.

_Treatment for Horses._ Alkalies, their carbonates and bicarbonates; alterative doses of aloes with alkalies; chalk, carbonate of magnesia; mineral acids; bismuth, arsenic, nux vomica, or strychnia.

=ACIDS, EFFECTS OF, ON VEGETATION.= This subject has been ably investigated of recent years by Dr Angus Smith and Mr Rothwell, and the practical importance of their labours is shown by the circumstance that an Act of Parliament passed in 1875 renders it penal for the proprietors of alkali works to condense not less than 95 per cent. of the hydrochloric acid evolved in the process of manufacturing 'soda,' also to allow air, smoke, or chimney gases to escape into the atmosphere containing more than one fifth of a grain of hydrochloric acid per cubic foot. Every owner of an alkali work is likewise required to 'use the best practical means of preventing the discharge into the atmosphere of all other noxious gases arising from such work, or of rendering such gases harmless when discharged.'

The injurious effects of acids on vegetation are indicated chiefly by the shrivelled-up appearance which the leaves of herbage, trees, &c., exhibit in the vicinity of chemical works in which the condensation of noxious gases (hydrochloric acid, sulphurous acid, sulphuric acid, sulphuretted hydrogen, nitric acid, and oxides of nitrogen and chlorine) is not effectually carried out. According to Mr Rothwell, 'in fields exposed to acid vapours handfuls of dead grass may be pulled up in the spring, smelling strongly of the vapour, and that trees, under similar influences, become bark-bound.'

The following is a list of trees arranged in the order of their susceptibility. (Rothwell.)

_Forest Trees._ Larch, spruce fir, Scotch fir, black Italian poplar, Lombardy poplar, ash, oak, elm, birch, alder, sycamore.

_Fruit Trees._ Damson, greengage, Halewood plum, Jacob plum, pears, apples, cherries.

_Shrubs, Evergreens, and Wild Plants._ British laurels, Portugal laurels, _Aucuba_ _Japonica_, Barberry evergreen, hazel, guelder rose, sloe thorn, hawthorn, raspberries, gooseberries, blackberries, gorse, hollies.

_Farm Crops._ Potatoes, mangel, white clover and rhubarb, red clover, trefoil, rye-grass, wheat, oats, barley, common turnips, swedes.

_Second list of Plants affected by Noxious Vapours, mixing the classes according to the effects produced on each._

I. Fern--only in the summer.

Scotch firs, spruce, and larches--a little in winter.

Clover (white and red), trefoil, rye-grass, poplars, hawthorn, potatoes--receive damage in winter to roots.

II. Wheat receives some damage in winter.

Oats in May, when in the grass state, soon receive damage.

Barley, mangel, common turnips, rhubarb.

III. Laurels (British and Portugal), aucubas, yews, holly, gorse--receive damage in winter, but more in summer.

Old grass meadows and pastures receive much damage in winter.

IV. Ashes, oaks, hazels, horse-chestnuts, walnuts, Spanish chestnuts, sloe thorn.

V. Swedish turnip and cabbages, damson, other fruit trees, beech, elm, birch, alder, sycamores.

=ACIDULÆ.= [L. pl.] In _medicine_, mineral waters rich in carbonic acid.

=ACIDULATED=. _Syn_. ACIDULATUS, L.; ACIDULÉ, Fr. Blended or flavoured with an acid; made slightly sour. See KALI (Acidulated), DROPS, LOZENGES, &c. In _chemistry_, the addition of an acid to a neutral or alkaline liquid until it reddens blue litmus paper.

=ACIDUM.= [L.] An acid.

=ACNE.= [_Syn._ PIMPLED FACE.] There are two forms of this affection. 1st. In young persons of both sexes; generally in phlegmatic habits. The disease shows itself by hard pimples, with a small black spot on the apex, unaccompanied with redness or inflammation at first, but after a while they become red and inflamed, and sometimes suppurate, with a greasy look of the skin between them. In this form of acne the black spots should be picked out with a needle or a small pair of tweezers. A long piece of thick matter, like a worm, is extracted; but is no worm. Afterwards wash the face with water in which a small piece of Quillar bark has been steeped, or with bitter almond emulsion, or borax, one drachm, water 4 oz. When there is no inflammation, use Eau de Cologne, or a few drops of oil of rosemary dissolved in spirit of wine, taking a small dose of magnesia in the morning, or milk of sulphur daily. When the pimples are very sluggish the cautious application of tincture of iodine, or of ointment of nitrate of mercury, will be found serviceable.

2nd. Arises from intemperance. In this case a gradual change of habits is essential. The use of soap should be avoided, and recourse had to warm fomentations of slippery elm, or thin oat gruel. The following should be applied to the pimples:--Cold cream, 1 oz., Goulard's extract 20 drops, mixed together; or lemon juice diluted, or solution of borax in water. The internal administration of the mineral acids combined with bitter tonics, or small doses of iodide of potassium, will be found effectual.

_Treatment._ Fomentations, poultices, chloride of zinc solution externally; sulphur and alteratives internally.

=ACOLOGY=. _Syn._ In _medicine_, the doctrine of, or a discourse on, remedies or the materia medica.

=ACONITE.= (-nite). _Syn._ ACON'ITUM, L.; ACONIT, Fr.: AKONITUM, EISENHUT, STURMHUT, Ger. Monkshood; wolfsbane. In _botany_, a genus of exogenous plants. _Nat. ord._, Ranunculaceæ; _Sex. syst._, Polyandria Trigynia. They are characterised by showy purple or yellow helmet-shaped flowers growing in panicles, deeply cut leaves, and perennial (usually) tap-shaped or tapering roots. The whole plant is highly poisonous, the roots being more poisonous than the leaves. In _medicine_ and _materia medica_, the plant Aconitum Napellus (which _see_).

_Symptoms._ Numbness and tingling in the mouth and throat, which are parched; followed by giddiness, dimness of sight, and (sometimes) delirium, but seldom complete coma; there is numbness and tingling of the limbs, a loss of power in the legs, (in some cases) frothing at the mouth, severe abdominal pains, nausea, vomiting, and diarrh[oe]a; tremors or twitchings of the voluntary muscles, (sometimes) convulsions (in animals, but not in man); sharp cries; pupil (generally) dilated, very rarely contracted; pulse fitful and sinking; skin cold and livid; difficulty of breathing; general prostration; loss of sensation or feeling, insensibility, general trembling, fainting, and sudden death. The eyes are often glaring; and, in some cases, the patient is completely paralysed, yet retains consciousness to the last. The case generally proves fatal in from 1 to 8 hours. If it last beyond this period there is hope of recovery. (Fleming.)

_Antidotes._ Ammonia, or brandy, with artificial respiration if necessary: cold affusion and friction, with warm towels to the back and limbs. See ALKALOIDS.

=ACONITE LEAVES= (B. Ph.). _Syn._ ACONITI FOLIA, L. The fresh leaves and flowering tops of _aconitum napellus_, Linn., gathered when about one third of the flowers are expanded, from plants cultivated in Britain.

_Char._ Leaves smooth, palmate, divided into five deeply cut wedge-shaped segments; excizing slowly, when chewed, a sensation of tingling. Flowers numerous, irregular, deep blue, in dense racemes.

_Prep._ Extractum aconiti.

=ACONITE ROOT.= (B. Ph.). _Syn._ ACONITI RADIX, L. The dried root of _aconitum napellus_. Imported from Germany, or cultivated in Britain, and collected in the winter or early spring before the leaves have appeared.

_Prep._ Aconitia, the active principle; Linimentum Aconiti, 1 ounce to 1 fluid ounce; Tinctura Aconiti, 54-1/2 grains to 1 fluid ounce.

_Char._ Usually from one to three inches long, not thicker than the finger at the crown, tapering, blackish-brown, internally whitish. A _minute_ portion, cautiously chewed, causes prolonged tingling and numbness.

=ACONITI FOLIA.= See ACONITE LEAVES.

=ACONITI RADIX.= See ACONITE ROOT.

=ACONITIA.= C_{30}H_{47}O_{7}N. (B. P.) _Syn._ ACONITIA, L. An alkaloid obtained from aconite.

Take of
Aconite root, in coarse powder, 14 pounds.
Rectified spirit }
Distilled water } of each
Solution or ammonia } a sufficiency.
Pure ether }
Diluted sulphuric acid}

Pour upon the aconite root three gallons of the spirit, mix them well, and heat until ebullition commences; then cool and macerate for four days. Transfer the whole to a displacement apparatus, and percolate, adding more spirit, when requisite, until the root is exhausted. Distil off the greater part of the spirit from the tincture, and evaporate the remainder over a water bath until the whole of the alcohol has been dissipated. Mix the residual extract thoroughly with twice its weight of boiling distilled water, and when it has cooled to the temperature of the atmosphere, filter through paper. To the filtered liquid add solution of ammonia in slight excess, and heat them gently over a water bath. Separate the precipitate on a filter, and dry it. Reduce this to coarse powder, and macerate it in successive portions of the pure ether with frequent agitation. Decant the several products, mix and distil off the ether until the extract is dry. Dissolve the dry extract in warm distilled water acidulated with the sulphuric acid; and, when the solution is cold, precipitate it by the cautious addition of solution of ammonia diluted with four times its bulk of distilled water. Wash the precipitate on a filter with a small quantity of cold distilled water, and dry it by slight pressure between folds of filtering paper.

_Characters and Tests._ A white, usually amorphous, solid, soluble in 150 parts of cold, and 50 of hot water, and much more soluble in alcohol and in ether; strongly alkaline to reddened litmus, neutralising acids, and precipitated from them by the caustic alkalies, but not by carbonate of ammonia or the bicarbonates of soda or potash. It melts with heat, and burns with a smoky flame, leaving no residue when burned with free access of air. When rubbed on the skin it causes a tingling sensation, followed by prolonged numbness. It is a very active poison.

=ACONITIA, CRYSTALLISED.= C_{27}H_{40}NO_{10}. Exhaust the root of wild aconite, carefully picked and powdered, with very strong alcohol, to which 1 per cent. of tartaric acid has been added. Distil at a gentle heat, and sheltered from the air, to recover the alcohol. Treat the extract with water to separate all the fatty and resinous matters. The solution which contains the aconite in the state of acid tartrate is first shaken with ether to remove colouring matters, and then the alkaloid is set free by the addition of alkaline bicarbonate, until the cessation of effervescence. A fresh treatment with ether of this alkaline solution removes the alkaloid, which crystallizes upon the concentration of the ethereal liquid, with an addition of petroleum spirit. The crystals are colourless tables, rhombic or hexagonal, according to the modifications produced principally in the acute angles. Crystallized aconitia is soluble in alcohol, ether, benzine, and chloroform; insoluble in petroleum oils and glycerine.

ACONITIA NITRATE, CRYSTALLISED. Crystallised aconitine q. s.; nitric acid, sp. gr. 1·442, q. s. Saturate the nitric acid with the aconitine and evaporate. Voluminous crystals are easily obtained (from 'Formulæ for New Medicaments adopted by the Paris Pharmaceutical Society').--'Pharm. Journal.' Owing to the decomposition which this alkaloid undergoes in the animal organism, as well as to its liability to decompose during the process of evaporation, and exposure to the air, it often becomes extremely difficult, if not impossible, to obtain it in a separate state in conducting a _post-mortem_ examination. The physiological effects seem to furnish the most prominent and characteristic evidence of its presence in such cases, or at any rate these may serve as a valuable guide to the toxicologist.

Uncrystallised aconitia is sometimes contaminated with delphinia, as well as with aconella, another constituent of aconite root. For the dissection of these see ALKALOIDS. One fiftieth of a grain of aconitia is stated to have killed a dog.

_Antidotes._ See ACONITE.

=ACONITIC ACID.= (Identical with _Pyrocitric Acid_.) An acid extracted by Peschier from _aconitum napellus_, and by Bracconnot from _equisetum fluviatile_. It exists in these plants chiefly in the form of aconitate of calcium.

_Properties._ A white, colourless, semi-crystalline mass.

=ACONITINA.= See ACONITIA.

=ACONITINE.= See ACONITIA.

=ACONI'TUM.= [L.] Aconite. The pharmacop[oe]ial name of _aconitum napellus_(see _below_).

=Aconitum Ferox.= (Ind. P.) _Habitat_. Temperate and sub-Alpine Himalaya, at 10,000 to 14,000 feet elevation, from Gurhwal to Sikkim.

_Officinal part._ The dried root (_Aconiti ferocis Radix_), in common with those of other Himalayan species, viz., _aconitum napellus_, _a. palmatum_, and _a. luridum_, constitutes the drug well known in the bazaars of Upper India under the Hindostani name of _Bish_ or _Bikh_.

It occurs in the form of tuberous roots of a more or less conical form, from two to three inches in length, and from half an inch to one inch in thickness at their upper end. They have usually a shrunken appearance, and are covered with a dark shrivelled bark; fracture shining and resinous; sometimes waxy, varying in colour from pale to deep brown. Some specimens are white and spongy; and these, it is asserted, are superior in activity to the more compact kinds. Inodorous; taste at first slightly bitter, leaving a peculiar sense of numbness on the tongue and fauces. Active principle, aconitia.

_Medical Properties and Uses._ Similar to those of _aconitum napellus_ of Europe. _Preparations._ This root may be advantageously used for the manufacture of aconitia, the proportion of this alkaloid being much larger than in the European drug; and also for the preparation of Linimentum Aconiti. From its greater activity, however, it is unsuited for the preparation of this tincture, which is intended for external use.

=Aconitum Hetorophyllum.= (Ind. P.) _Habitat_. Western temperate Himalaya, at 8000 to 13,000 feet elevation; from Indus to Kumaon. _Officinal part._ The dried root (_Aconiti heterophylli Radix_). Ovoid tuberous roots, tapering downwards to a point, from one to one and a half inches or more in length, and from three eighths to half an inch in thickness. The surface, which is covered with a thin greyish epidermis, is slightly wrinkled longitudinally, and marked here and there with root scars. It is inodorous, and of a bitter taste, devoid of acridity. Does not contain aconitia. It may be readily distinguished from other roots sold in the bazaars under the same vernacular name (Atis) by its characteristic bitterness. _Properties._ Tonic and antiperiodic. It may be administered internally with safety, as it contains no poisonous principle. _Therapeutic uses_. In convalescence after debilitating diseases, and in intermittent and other paroxysmal fevers, it has been found an efficient remedy. _Doses._ Tonic, 5 to 10 grains thrice daily; antiperiodic, 20 to 30 grains of the powdered root every three or four hours, irrespective of the presence of pyrexia.

=Aconitum Napell'us.= [Linn.] _Syn._ ACONI'TUM, Ph. L., E., & D.; ACONITNAPÈL, CHAPERON DE MOINE, Fr.; EISENHUT, BLAUERSTURMHUT, Ger. Early blue wolfsbane, or deadly aconite. _Hab._ Various parts of Europe; grows wild in England, flowering in June and July. The fresh and dried leaves (ACONITI FO''LIUM), Ph. L. & E. The root (ACONITI RA'DIX), Ph. L. & D. This is the species of aconite ordered in the pharmacop[oe]ias, and commonly used in medicine. When chewed it imparts a sensation of acrimony, followed by a pungent heat of the lips, gums, palate, and fauces, which is succeeded by a general tremor and chilliness. The juice applied to a wound or the unsound skin affects the whole nervous system. Even by remaining long in the hand, or on the bosom, it produces unpleasant symptoms. Fatal cases of poisoning, by eating the root in mistake for horseradish, have been common of late years. The two roots may be, however, easily distinguished from one another; when scraped aconite emits an earthy, and horseradish its well-known pungent odour. Moreover, the shape of the roots is very different. In the accompanying figure _a_ represents aconite root, and _b_ horseradish root.