Officinal. Atropa Belladonna and its extract.

30. Delphia, an alkali, the active principle of Delphinium Staphisagria. (See Part ii.)

31. Hyoscyama, an alkali, the active principle of Hyoscya-mus niger. (See Part ii.)

32. Daturia, the active principle of Datura Stramonium.

33. Veratria, an alkali, the active principle of Veratrum album, and Colchicum autumnale. (See Part ii.)

34. Strychnia, an alkaline substance, the active principle of Nux vomica. It is white, granular, inodorous, extremely bitter, insoluble in ether, slightly soluble in cold water, but very soluble in alcohol. Forms a class of salts with acids, which are most virulent poisons.

35. Conia, the active part of Conium maculatum; resembles a volatile oil, of a pale yellow colour : is rapidly decomposed when exposed to the air.

Officinal. Conium and its preparations.

36. Piperina, one of the active principles of Black Pepper and of Chamomile flowers.l

37. Elating the active principle of Elaterium. (See Mo-mordica, Part ii.)

38. Cytissina, the active principle of Arnica montana, and Asarum Europaeum.

39. Balsams resemble resins in their appearance; have a strong aromatic odour; yield benzoic acid when heated, or dissolved in sulphuric acid; and when treated with nitric acid, yield artificial tannin.

Officinal. Balsams of Peru, tolu, benzoin, storax.

40. Gum resins resemble resins in their appearance; but they are odorous, and form milky solutions with water, and transparent solutions with alcohol. They are soluble in alkalies.

Officinal. Ammoniacum, galbanum, scammony, assafœtida, myrrh, sagapenum, gamboge.

41. Wood, which forms the support of all vegetables, is composed of tasteless fibres, insoluble in water and alcohol, but soluble in weak alkaline ley, and in nitric acid, yielding oxalic acid. When distilled per se, at a red heat, it leaves much charcoal and acetic acid.

i. Solid animal matters.

1. Albumen when dried is a brittle, transparent, glassy substance, resembling gum in appearance. It is soluble in cold water; and when the solution consists of one part of dry albumen and nine of water, heat coagulates it into a firm, white, solid mass. Alcohol, ether, the strong acids, bichloride of mercury, many metallic oxides, and tannin, also coagulate the solution.

Officinal. White of egg, hartshorn shavings.

2. Solid oils are composed, like the other fixed oils, of a solid and a fluid substance, which Chevreul has named Stearin and Eldin.

1 I first ascertained its presence in Chamomile flowers,

Varieties, a. Spermaceti. (Part ii.) b. Fat is an odorous, insipid, white, crystalline substance; greasy to the touch; melts at 140°; vaporized at 400°, the vapour being inflammable; insoluble in water, alcohol, and ether; combines with alkalies, and forms soap; and is decomposed by strong acids.

Officinal. Lard, mutton suet, fat.

3. Cantharidin is the active principle of Spanish flies. (See Part ii.)

Officinal. Cantharis officinalis. Mylabris variabilis.

4. Cochinilin is the colouring principle of the Cocus Cacti, (See Part ii.)

5. Castor. (Ibid.)

6. Musk. (Ibid.)

7. Bones and Shells. (Ibid.)

8. Horn. (Ibid.)

Combination Of Solids With Solids

Although solid bodies may be made to enter into combination with one another, yet all do not combine in the same manner, and under similar circumstances. Thus, some unite in any proportion, and some in certain determinate proportions only; while others will not combine with each other under any circumstances.

1. Table of the principal pharmaceutical Solids which have been ascertained to be capable of uniting in any proportion.

Sulphur with phosphorus.

Metals with most metals.

Protoxide of antimony with sulphuret of antimony.

Earths with earths.

Earths with some metallic oxides.

Some earths with fixed alkalies.

Solid oils with each other, and with bitumen. All the products are solids, except those resulting from the union of sulphur and phosphorus, which are liquid.

None of these solids combine spontaneously, even although placed in contact; but require to be mixed, and exposed to a degree of heat capable of melting one or both of them; in which case, the caloric breaking the force of the cohesive attraction which retains the particles of the solids in the aggregate state, the atoms of the one substance are brought into immediate contact with those of the other, or within the sphere of the attraction of affinity, which consequently acts and produces the new compound. The compounds do not very materially differ in their properties from their constituents, except the compounds of iron with carbon, and some of the earths with each other. The combination is generally accompanied with a change of density.

2. Table of the principal pharmaceutical Solids which have been observed to unite only in determinate proportions.

Iodine with metals. Sulphur with metals. Fixed alkalies? Phosphorus with carbon.

----------------------metals.

Acids with alkalies. -------------metallic oxides, etc.

These enter into more intimate union than the preceding. They, however, do not unite when both bodies remain in the solid state; "except sulphur and the fixed alkaline hydrates1, some acids, and a few hydrates of metallic oxides:" hence they are brought into union, either by fusion, or by solution in water, or in some other liquid menstruum. By the first mode "sulphur is made to combine with metals, and fixed alkalies, and phosphorus with metals:" by the second, the acids are combined with the alkalies, and the other metallic oxides. The mode of union resembles that of liquids with solids in every respect.

It is important to ascertain the proportions in which these bodies unite, and their change of density. Berthollet is of opinion, that sulphur may unite indefinitely with the metals, the proportion of sulphur varying indefinitely in many native sulphurets; but Dr. Thomson2 maintains the contrary opinion, owing to the circumstance, "that when sulphur and a metal are fused together, we obtain always the two bodies combined in determinate proportions."

Table 1. exhibits the composition of the iodides; table 2. that of the sulphurets of the officinal metals.

The first column in the table of the sulphurets gives the specific gravity of the sulphuret; the second, the weight of sulphur united to 100 parts of the metal; the third, the atomic equivalents; the fourth, the colour of the sulphuret.

1 These are alkalies in the crystalline form, or containing water solidified.

2 System of Chymistry, 4th edit. iii. 136.

Table 1.- Iodides

Table 2.- Sulphurets

The metallic sulphurets are rarer than the mean of their components, owing to the substances expanding, during their union, sometimes more than one fifth of the whole. Pyrites, however, is an exception, its specific gravity being greater than the mean.1

Nothing precise is known of the other combinations of sulphur, nor of those of phosphorus with solid bodies.

The combinations of the acids with alkalies, earths, and metallic oxides, are well understood. When an acid and an alkali are mixed together, we find that, after several small additions of the alkali to the acid, diluted with a little water, the mixture still retains acid properties; but by continuing to add the alkali these disappear, and alkaline properties are acquired by the next addition that is made; the acid or the alkaline properties of the compound, therefore, predominate according to the proportions of each; but there are certain proportions, according to which they destroy, by their union, the properties of each other, so that neither predominates. In this case they are said to neutralize each other; the products are named neutral salts, and the proportions in which the acids and alkalies unite to form neutrals are fixed and determinate.

All salts, however, are not neutrals; but in some, the proportions of the acid,-in others, that of the base, predominate. The former, which are named super-salts, or bisalts, are supposed to be compounds of two or more atoms of the acid with one of the base; and the latter, which are named sub-salts, of two atoms of the base with one of the acid. Thus, bitartrate of potassa consists of one atom of potassa = 47.15 united to two of tartaric acid = 132.96, with 1 of waters 9.; making the equivalent of the salt = 89.11; or, by weight, of 5.23 parts of base, and 100 of acid 2; while carbonate of potassa consists of one atom of potassa = 47.15, and one of carbonic acid =22.12, making the equivalent of the salt=69.27, or, by weight, of 2.75 of acid and 6.00 of base. Triple salts are composed of one acid united to two bases at the same time,-as the tartaric acid, for instance, with potassa and soda, to form the tartrate of potassa and soda; the equivalent of which in its crystalline state is = 283.41.

The metalline salts are seldom neutral, having generally an excess either of acid or of base.