as the original amide compounds. These amides, when treated with sulphide of hydrogen, yield the aldehyde, but with sulphur substituted for the oxygen.

499. When benzoic aldehyde is evaporated with hydrocyanic and hydrochloric acids, we obtain formobenzoic acid:

Formobenzoic acid.

2 C, H, O+ 2HCN+4H,O=2N H2+ C1s H1 Oc

6

500. An atom of hydrogen in the radical of these aldehydes can be replaced by N O,. Example:-Aldehyde of nitrobenzoyl, H, C, H, (NO)O. These compounds are transformed by potash into the corresponding nitro-acids; and by ammonia into nitro-amide compounds.

FOURTH CLASS OF ALDEHYDES.

(General formula of the acid radicals in this class of aldehydes, CnH2n-11 O.)

501. The hydrides of the alcohol radicals and the alcohol metals corresponding to this class of aldehydes have not been isolated, and only one aldehyde belonging to the class has been discovered; it bears, as the student will see, the same relation to the preceding class as the allyl class does to the vinic one.

Hydride of cinnamyl (oil of cinnamon), H, C, H, O.

502. Essence of cinnamon and essence of cassia consist chiefly of this aldehyde.

503. Properties.-It behaves with oxygen, potash, and the bisulphites like the previous aldehydes. It is often converted, in its decompositions, into hydride of benzoyl, and the hydride of benzoyl can also be converted into it; for instance, if hydride of cinnamyl be boiled with nitric acid, hydride of benzoyl is evolved, and benzoic acid is found in the solution; and if hydride of benzoyl be dissolved in aldehyde, and the solution saturated with hydrochloric acid gas, and afterwards distilled, oil of cinnamon is found in the distillate; hydride of cinnamyl may, in fact, be regarded as hydride of benzoyl, in which an equivalent of hydrogen has been replaced by an equivalent of acetyl. Example:-H, C, H1 (C2 H ̧) O.

FIFTH CLASS OF ALDEHydes.

(General formula of the acid radicals in this class of aldehydes, Ca Han- 0..)

The

504. The hydrides of the alcohol radicals and the alcohol metals of this class have not been isolated. aldehydes of this class differ only from those in the third class in the quantity of oxygen they contain; the relative proportion of the carbon and hydrogen is the same, and they increase also, like the third class, in the proportion of CH2.

Hydride of salicyl (salicylous acid), H, C, H, O,
Hydride of anisyl -
H, C, H, O2.

505. Preparation.-Salicylous acid is found as the chief ingredient in the essence of meadowsweet; it is separated from the hydrocarbon which accompanies it by treating the crude essence with solution of potash; the acid combines with the potash, whilst the hydrocarbon is distilled; the potash compound, on being distilled with a slight excess of dilute sulphuric acid, yields the hydride pure. It is also obtained by distilling one part of salicine, one part of bichromate of potash, two and a half of oil of vitriol, and twenty of water, together. When oil of aniseed is acted upon by dilute nitric acid, a reddish oil is obtained, consisting of a mixture of anisic acid and hydride of anisyl; if the oil, after being washed with a weak solution of potash in order to remove the anisic acid, be cautiously distilled, the hydride passes over pure.

506. Properties.-The hydride of salicyl possesses the characters of an acid; it decomposes the carbonates with effervescence, yielding crystallizable salts; one or more atoms of hydrogen in the radical of salicylous acid can be replaced by chlorine, bromine, or N O2; the bodies produced by these substitutions likewise possess acid properties, and are capable of forming salts. One or more atoms of hydrogen in the radical, anisyl, can also be replaced by Cl, Br, or N O2; but this hydride has not been so much studied as salicylous acid. Both aldehydes combine with ammonia and with the bisulphites.

(3.) KETONES (ACETONES).

507. The constitution of these bodies is still, like the constitution of the aldehydes, a matter of doubt. Some

chemists represent them on the type water; others represent them on the hydrogen type. We will formulate acetone, the best known member of the family of the ketones, on both these types, so as to make the student acquainted with the prevailing views on the constitution of this class of bodies. On the type of water the formula CH of acetone is 0. According to this formula the CHS ketones are bodies in which the atoms of hydrogen in water have been all replaced by different hydrocarbon radicals. On the type of hydrogen the formula of acetone C, H, O.

is

CH According to this formula, the ketones are conjugated aldehydes, in which the equivalent of hydrogen is replaced by one of the alcohol radicals.

508. Preparation of the ketones.-The ketones are prepared by submitting to destructive distillation a metallic salt, in the anhydrous state, of the corresponding acid of the series. The acid is decomposed into the ketone and carbonic acid; this latter body remains combined with the metal, if it be one of the alkaline metals, or a metal of the alkaline earths; if not, it is evolved along with the ketone. We will give the decomposition which occurs when acetate of lime is submitted to destructive distillation, as the representative of the decompositions which the salts of the other acids of the series undergo.

509. As the ketones have only been very incompletely studied, we shall not describe their properties, but simply give the formula of a few of them.

Ketones corresponding to the first class of alcohol radicals, and to the first class of aldehydes.

* Fridel has converted acetone, by the direct addition of hydrogen, into propylic alcohol, or an alcohol isomeric with it; he effected this conver sion in the same way as Wurtz eflected the conversion of aldehyde into alcohol, viz., by treating an aqueous solution of acetone with sodium amalgam.-See Repert, de Chimie, vol. iv. p. 351.

510. Ketones corresponding to the alcohol radicals of the third classs, and to the aldehydes of the third class. Benzophenone . Cε H2, C, H, O

511. The acetones combine, like the aldehydes, with the alkaline bisulphites.

512. The acetones appear to combine with ammonia, like the aldehydes, forming, like them, with the ammonia, basic compounds. As yet only acetone has been submitted to this process.

2 H, N = 3 C, H, O = (C, H;,)***} N2 + 3 H, O.*

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EXERCISE.

133. Write out the formula for the following substances: -Propionic aldehyde, valeraldehyde, capric aldehyde, enanthylic aldehyde, butyracetone (butyrone), valeracetone, pelargonic aldehyde, enanthylone.

DOUBLE MOLECULE.

H2, H2.

POSITIVE Group.

513. This group embraces (1) The biatomic metals. (2) The radicals of the biatomic alcohols. (3) Compounds of metals with monatomic alcohol radicals.

(1.) HYDRIDES OF METALS (PRIMARY DERIVATIVES). METALS PROPER (SECONDARY DERIVATIVES).

514. Primary derivatives.-No hydride of any of the metals is known which is formed on the double molecule.† 515. Secondary derivatives.-Palladium, platinum, titanium, and tin are the principal biatomic metals; the first two we have noticed act sometimes as monatomic metals, and the last two sometimes act as tetratomic metals.

The student must omit the Exercise, and the rest of this chapter, and pass on to Chapter VIII., commencing at par. 511.

Quite recently Wanklyn and Carius have obtained hydride of iron, which has the following composition, Fe, H. They obtained it by acting upon zinc-ethyl with iodide of iron; thus,

ZD, (C2 H)2 + Fe, I2 = 2 Zn I + Fe, H2 + 2 (C2 H ̧).

2

(2.) RADICALS OF THE BIATOMIC ALCOHOLS.

(General formula, Ca Han)

516. Very different views are taken of the rational constitution of this class of hydrocarbons. Liebig regards them as the hydrides of the radicals, C, Han-1. They might also be regarded as the hydrides of the alcohol radicals of the second class; for instance, propylene, C, H, might be regarded as the hydride of allyl, H, C, H,. But it will be seen, as we proceed, that there is good reason for viewing them as positive radicals, capable of replacing, and possessing the functions of, two atoms of hydrogen; viewed in this light they are diatomic radicals.

517. When these bodies are submitted to the action of chlorine, several chlorine derivatives can be obtained; but in order to show the student how the constitution of these bodies was unravelled, we will here direct his attention to only one of these chlorine compounds at present, and we will take one member (ethylene, C, H.) of the group, as less confusing to the student than if we were to allude to the entire group. When equal volumes of ethylene and chlorine are added together, they combine, and give rise to a compound called Dutch liquid, which may be formulated thus, C, H, Cl,; there has, therefore, been a direct combination between the chlorine and the hydrocarbon, unattended with any substitution; if this compound be treated with an alcoholic solution of potash, it parts with the elements of hydrochloric acid; it was therefore inferred that the rational formula of this chlorine compound was not C, H, Cl, but C, H, Cl, H Cl. This was the view chemists took of the constitution of Dutch liquid, until M. Wurtz proved, by the most elegant and convincing experiments, that its correct formula is C, H, Cl2.

Constitution of Dutch liquid, according to M. Wurtz.

518.-1st. If we treat ordinary vinic alcohol with pentachloride of phosphorus, we obtain chloride of ethyl, thus:Chloride of ethyl.

C2H2O+PCI PCI, O + HCl + C, H, Cl.

=