and final precipitation of a part of the salt with ether, until the zinc salt remaining dissolved is obtained completely amorphous on evaporation. The free acid is then liberated by hydric sulphide.

Ethylene lactic acid forms a syrup, closely resembling ethylidene lactic acid. Its alkali salts are very soluble; the sodic salt yields, on complete evaporation on the water bath, a solid crystalline mass, soluble in alcohol and crystallising from the boiling alcoholic solution in indistinct forms.

Zincic ethylene lactate is completely amorphous; it is somewhat decomposed at 100°, becoming yellow-coloured, so that it can only be completely dried in vacuo. It gives at first a transparent gummy mass, which becomes turbid on complete drying. Its composition is then (C3H5O3)2Zn.

By oxidation with nitric acid or with chromic and sulphuric acids it yields no acetic acid, but carbonic anhydride and oxalic acids. A mixture of paralactic and ethylene lactic acids, such as is obtained from extract of meat, on the other hand, yields malonic acid, which can only be formed from the ethylene lactic acid :

HO.CH,.CH,.CO.OH + 20 = HgO + HỌ.CO.CH,.CO.OH.

(Malonic acid.)

By heating with hydriodic acid it does not yield crystalline iodo-propionic acid.

4. Hydracrylic Acid.

744. If glyceric acid, obtained by the oxidation of glycerine, be heated in syrupy solution with phosphorus iodide, a violent reaction occurs with evolution of hydriodic acid, and on cooling the mass solidifies to a crystalline pulp of ß-iodo-propionic acid:

C3H6O3HI = I2+ 2H2O + C2HIO.

2

The same body is obtained by heating acrylic acid and a solution of hydriodic acid at 120° :

It crystallises in large, colourless, brilliant plates, which melt at 82° and are difficultly soluble in cold, readily in hot, water. By heating with concentrated hydriodic acid to at least 180° it is converted into propionic acid.

By treatment with chlorine water iodine is eliminated and ẞ-chlorpropionic acid formed:

2C,H,IO2+ Cl2 = I2 + 2C3H5ClO2,

which forms leafy crystals melting at 40.5°, and which can also be prepared by combining acrylic and hydrochloric acids.

B-Brom-propionic acid can be prepared in exactly analogous manner to the last; it forms crystals melting at 61.5°.

745. On adding freshly precipitated argentic oxide to a hot solution of B-iodo-propionic acid, as long as argentic iodide separates, hydracrylic acid is formed:

C2H2IO2+ AgOH= AgI + C2H5(OH)O2.

The liquid is treated with sulphuretted hydrogen to remove excess of

silver, and the filtrate saturated when hot with zincic carbonate. By slow evaporation zincic hydracrylate is obtained in beautiful prisms, from which pure hydracrylic acid can be separated by hydric sulphide.

Hydracrylic acid is syrupy, like the other lactic acids, does not yield ethereal anhydrides on heating or acetic aldehyde on dry distillation, but is converted into water and acrylic acid :

C3H6O3 = H2O + C3H4O2.

By careful oxidation with chromic acid or nitric acid it is converted into carbonic anhydride and glycollic acid, the latter being readily further oxidised to oxalic acid.

The constitution of hydracrylic acid is not yet sufficiently clear, but the results of oxidation and other considerations render probable the formula:

CH2.OH

H.C

H.C OH

By heating with hydriodic acid it is readily reconverted into ẞ-iodopropionic acid:

=

C3H6O3 + HI H2O + C2H2IO2.

The salts of hydracrylic acid differ very essentially from those of all the isomeric acids.

The sodic salt separates from boiling nearly absolute alcohol in colourless anhydrous crystals of the formula C3H,O,Na, melting at

143°.

Calcic hydracrylate, (C3H5O3)2Ca, 2H,O, crystallises in rhombic prisms, which readily part with their water of crystallisation.

Zincic hydracrylate, (C3H5O3)2Zn,4H2O, crystallises in large wellformed triclinic prisms, and is soluble in somewhat less than its own weight of cold water. On mixing solutions of equal molecules of the zincic and calcic salts, crystalline crusts of the difficultly soluble double salt, (C3H5O3)2Zn,(C,H,O3)2Ca, separate. All salts of hydracrylic acid lose water when heated to 180°-200°, and are converted into a mixture of salts of acrylic acid, C3H,O, and diacrylic acid, CH.04.

746. If ẞ-iodo-propionic acid be heated with ammonia solution, it yields ẞ-amido-propionic acid, C3H5(NH2)O3 (or doubled), isomeric with alanine, which crystallises in colourless monoclinic prisms. It is readily soluble in water, difficultly in alcohol, sublimes at 170° on careful heating, and carbonises at higher temperatures.

Hydroxy-butyric Acids, C,H,03.

747. Four isomeric bodies of this formula have been obtained. 1. a-Hydroxy-butyric Acid. On heating butyric acid for some time with a molecule of bromine to 120°-130° in sealed glass tubes, there is formed principally a-brom-butyric acid, CH3.CH2.CH Br.CO.OH, as a non-crystallisable oily liquid, which boils at 217° with partial decomposition, and yields an ethylic salt boiling at 172°. On heating the solutions of its alkaline salts, they are decomposed into metallic bromide and a-hydroxy-butyric acid, CH3.CH2.CH(OH).CO.OH, which

is purified by conversion into the zinc salt, very difficultly soluble in cold water, and the free acid separated therefrom in the usual manner. It crystallises in starlike groups of needles or prisms, melts at 43°-44°, and deliquesces in air. At higher temperatures it loses water and is converted into its ethereal anhydrides. Its zinc salt has the formula (C,H,O3)2Zn,2H2O.

By decomposition of a-brom-butyric acid with ammonia it yields CH,.CH,CH.NH,

amido-butyric acid,

COO H

(§

, corresponding to glycocine

and alanine, which crystallises in small needles and leafy crystals. 2. B-Hydroxy-butyric acid, CH3.CH(OH).CH2.CO.OH, is formed by oxidation of its aldehyde, aldol ($ 656). It is prepared synthetically from propylene hydrate chloride (§ 496) by heating with potassic cyanide and boiling the resulting solution of propylene hydrate cyanide, CH3.CH(OH).CH2.CN, with potassic hydrate.

It is most readily obtained by the action of water and sodium amalgam on ethylic aceto-acetate :

CH3.CO.CH2.CO.OC2H5 + Na2 + 2H2O

=CH.CH(OH).CH,.CO.ONa + NaOH + HỌ.C,H.

Its sodic salt crystallises from nearly absolute alcohol in fine prisms, which deliquesce in air. The calcic, zincic, and plumbic salts are amorphous, very soluble in water and also in alcohol.

At higher temperatures it decomposes into water and a-crotonic acid:

CH,.CH(OH).CH,CO.OH=CH,CH:CH.CO.OH + H,O.

3. y-Hydroxy-butyric acid, CH(OH).CH2.CH.CO.OH, obtained by action of baric hydrate on succinic aldehyde; it yields succinic acid on oxidation.

4. a-Hydroxy-isobutyric acid, (CH3)2: C(OH).CO.OH, also termed butyl lactic acid, dimeth-oxalic acid, or acetonic acid, is prepared by several methods.

Isobutyric acid is converted into a-brom-isobutyric acid by heating to 140° with bromine. This is crystalline, melts at 45°, and decomposes on distillation. When mixed with a small quantity of water it becomes oily, probably from formation of the trihydrate :

(CH3)2CBr.C(OH)3,

but again solidifies after some time in a dry vacuum; it is but little soluble in cold water. By boiling with alkalies it is converted into a-oxyisobutyric acid.

As dimeth-oxalic acid this latter is obtained by heating oxalic acid with methylic iodide and zinc (§ 705, 8), as acetonic acid from acetone, hydrocyanic and hydrochloric acids (§ 705, 6), as butyl lactic acid by oxidation of isoamylene glycol with nitric acid.

a-Hydroxy-isobutyric acid crystallises in colourless soluble prisms, which melt at 79° and sublime even at 50° in needles. It evaporates so readily in aqueous vapour that nothing is left on evaporation of an aqueous solution. By gentle oxidation it is first converted into acetone and carbonic anhydride. Its salts are all crystalline, and its

zinc salt, like those of all u-oxy-acids, is very difficultly soluble in cold water.

748. Nitrile and urea derivatives of a-hydroxy-isobutyric acid can be prepared from acetone.

The latter unites directly with anhydrous hydrocyanic acid to form the liquid nitrile, (CH3)2:C(OH).CN, which on distillation is resolved into its components, similarly to ethylidene hydrate cyanide (§ 712).

If acetone be mixed with finely powdered potassic cyanide, and hydrochloric acid added slowly until all the latter is decomposed, the nascent elements of a molecule of hydrocyanic acid unite with two molecules of acetone, yielding diacetone-cyanhydrin :

2(CH3), :CO + KCN + HCl = KCl + (CH,)2:C.0.C:(CH3),

ÓN ÓH

CN OH

This latter crystallises in beautiful brilliant prisms, which sublime readily, melt above 130°, and are resolved by strong acids into ammonia, acetone, and a-oxyisobutyric acid :

(CH3)2 C.O.C:(CH3)2 + HCl + 2H2O = (CH3)2C.OH

CN OH

+ CO(CH3)2 + NH ̧CI.

CO.OH

A mixture of acetone with potassic cyanide and isocyanate yields, on treatment with hydrochloric acid, acetonyl urea, corresponding to hydantoin (§ 724), and lactyl urea (§ 739) :

(CH3):C.NH

(CH3)2CO + HCN + HNCO =

=

CO

CO.NH

It is crystalline, melts at 175°, sublimes in fine brilliant needles on careful heating, and on heating with baric hydrate solution yields the (CH,),:C.NH.CONH,

amorphous salt of acetonuramic acid,

CO.OH

cor

responding to hydantoïc acid, which in the free state decomposes into water and acetonyl urea. By boiling with acids the latter is resolved into ammonia, carbonic and a-oxyisobutyric acid.

Hydroxy-valeric Acids, C5H1003.

749. Only three of the numerous theoretically possible oxyvaleric acids are known.

1. a-Hydroxy-isovaleric acid, (CH3)2: CH.CH(OH).CO.OH, is formed from a-brom-isovaleric acid, (CH3)2: CH.CHBr.CO.OH (obtained by heating isovaleric acid with bromine), by boiling with moist argentic oxide. It crystallises in large colourless tables, melting at 80° and slowly subliming below 100°, which dissolve readily in water, alcohol, and ether. A mixture of chromic and sulphuric acids oxidises it to isobutyric acid, carbonic anhydride, and water. By boiling ammonic a-brom-isovalerate with ammonia, a-amido-isovaleric acid,

(CH3)2:CH.CH.NH,

CO.O H

is formed, which crystallises in colourless

leaves, somewhat sublimable. It behaves towards acids and bases in similar manner to alanine, glycocine, &c. Apparently the same body has been prepared, under the name of butalanine, from the spleen and pancreas gland of oxen.

CH3.CH,
CH

2. Eth-meth-oxalic acid, 2>C(OH).CO.OH, the a-hydroxy substitution product of eth-meth-acetic acid, is obtained by heating together a mixture of ethylic oxalate, ethylic iodide, and methylic iodide with zinc, in the form of its ethylic salt (boiling point 165°). This, on saponification with alkalies, decomposition of the salt with sulphuric acid, and extraction with ether, yields the free acid in readily soluble crystals, melting at 63°.

3. B-Hydroxy a-methyl butyric acid:

CH3.CH(OH).CH(CH3).CO.OH.

The sodic salt of this acid is obtained by the action of sodium amalgam on an aqueo-alcoholic solution of ethylic aceto-meth-acetate :

The free acid does not crystallise, nor has it been as yet obtained anhydrous, as on drying it is gradually converted into a dehydro-acid. On distillation it yields a dimeth-acrylic acid, CH3.CH:C(CH3).CO.OH.

Hydroxy-caproic Acids, C6H1203.

750. 1. a-Oxyisocaproic acid, leucic acid:

(CH3)2:CH.CH,.CH(OH).CO.OH.

Isovaleric aldehyde ammonia yields, on treatment with hydrocyanic and hydrochloric acid, a-amido-isocaproic acid :

(CH3)2:CH.CH,.CH . NH,

CO.Ó H

which is converted into the oxyacid by treatment with nitrous acid. The oxyacid crystallises in colourless needles, readily soluble and melting at 73°. Its salts are mostly difficultly soluble.

A body of great physiological importance, known as leucine and obtained as a decomposition product of albuminoid bodies, is probably identical with a-amido-caproic acid. It is obtained from nearly all proteoids and from gelatine (in the latter case together with glycocine) by putrefaction, by action of pancreas ferment, and by boiling with alkalies and strong acids; it occurs in small quantity in some animal organs.