Secondary alcohols are correspondingly prepared by hydrogenising ketones. Primary alcohols can be converted into those secondary alcohols which have the OH group attached to the carbon atom next to the primary position in the following manner :-The primary alcohol is converted by dehydrating agents (by heating with concentrated sulphuric acid or zincic chloride) into a hydrocarbon, CnH2n (olefine): CmH2m+1 CmH2m + 1

and the latter then gently heated with concentrated hydriodic acid. One molecule of this is taken up, the iodine going into the secondary, the hydrogen into the primary, position:

The secondary alcoholic iodide is then converted into acetate by heating with potassic acetate, and finally into the secondary alcohol by treatment with potassic hydrate.

This transformation can be still more simply effected by absorbing the olefine in concentrated sulphuric acid. By the same law of the easier combination of negative elements or radicals to an intermediate than to a terminal carbon atom, the acid sulphate formed is that of the secondary alcohol:

which by treatment with an alkali, or by boiling with a large excess of water, yields the secondary alcohol:

CH.O.SO.OH + H2O = CH.OH + HO.SO.OH + (x-1) H2O

CH.O.SO.OH

Tertiary alcohols can be similarly prepared from primary alcohols in which the CH2.OH group is directly united with a tertiarily combined carbon atom:

Just the same result is arrived at by the use of sulphuric acid :

CH3 CH3

Č.OH + KO.C2H2O

A general method of preparing tertiary alcohols is by the action of the chlorides of monobasic acid radicals on the zinc compounds of the alcohol radicals:

When the product of this reaction is heated with water, a paraffin, zincic hydrate, and a tertiary alcohol result:

164. The homologous series CnH2n+ 20 or CnH2n+1.OH includes members of from one to thirty carbon atoms, together with their

isomers. In many cases members are still missing. The known members are:

As

165. Carbinol, commonly called wood spirit, results from the dry distillation of wood; the aqueous layer of the distillate contains in addition several other bodies, such as acetic acid, acetone, &c. the boiling point of carbinol is considerably lower than that of water, on distilling the wood-tar water-previously mixed with lime to fix the acetic acid-all the methylic alcohol is contained in the first tenth of the distillate. This first fraction still contains, however, acetone and water; to remove the latter it is rectified over quick-lime; the distillate containing the wood spirit and acetone is added to fused calcic chloride, which combines with the first, so that the unchanged acetone, which is readily volatile, may be driven off by heating in a water bath. The residue, the compound of carbinol and calcic chloride, is now mixed with water, whereby, with formation of CaCl2,6H2O, the carbinol is set free, and on distillation passes over, together with a little water. By repeated rectification over quicklime it is obtained anhydrous. In the preparation so obtained there are still some impurities adhering obstinately to it, which communicate a burning taste. It is obtained quite pure by conversion into its oxalate, which, being crystallisable, is easily purified, and then retransformed into the alcohol by potassic hydrate,

Carbinol can also be prepared from the ethereal oil of gaultheria procumbens (the North American winter-green shrub). This contains methylic salicylate, mixed with hydrocarbons; the first, on boiling with an alkali, yields a salicylate and methylic alcohol.

Carbinol is a colourless, mobile, spirituous-smelling liquid, of sp. gr. 814 at 4°; it boils at 60°, is readily inflammable, and burns with a slightly luminous flame. It mixes in every proportion with water, ethylic alcohol, and ether, in the first case with diminution of volume and evolution of heat. By oxidising agents, e.g. air in contact with platinum black, it is converted into formic aldehyde and formic acid. By passing its vapour over heated soda lime a formate is produced :

CH3.OH + NaOH = CHO.ONa + 2H2.

It is a good solvent for many substances insoluble in water, such as fats or ethereal oils, and for many salts; e.g. calcic chloride, especially on heating, is dissolved by it in considerable quantity; the saturated liquid, on cooling, gives leafy crystals of a compound, in which methylic alcohol is united to calcic chloride like water of crystallisation. This compound is not decomposed at 100°.

CH3

Methyl Carbinol, or Ethylic Alcohol, C2H,.OH CH2

=

он

166. Ethylic alcohol, or spirits of wine, more commonly known as alcohol only, results from the fermentation of many saccharine bodies, whereby these nearly entirely decompose into carbonic anhydride and alcohol:

C6H12O62C2H60 + 2CO2.

There are also some other products formed, such as succinic acid, glycerine, and higher members of the alcohol series, which latter are known as fusel oils or fusel alcohols.

The ferment essential to the alcoholic fermentation is yeast, a onecelled organism, propagating by budding, which, under favourable conditions, causes the decomposition of the sugar to occur with great quickness, and with evolution of heat, when placed in contact with its solutions. To the conditions necessary belong the temperature, which must not be below 0° nor above 35°; the presence both of certain mineral substances (especially phosphates) and of nitrogenous organic matters, which serve as food for the yeast; and, finally, sufficient dilution of the sugar solution. If this latter be too concentrated it is either not at all transformed, or the fermentation ceases in consequence of the death of the yeast cells. A liquid containing more than 20-22 % of sugar cannot be completely fermented by yeast. Many poisonous substances, e.g. phenol, even in small quantity in an otherwise favourably mixed solution, prevent fermentation by killing the yeast cells.

Alcohol, which boils at a lower temperature than water, can be obtained more pure from the fermented liquid by fractional distillation. It is then found in the first fractions, whilst water and the non-vola

tile matters-namely, the yeast and the marc-remain behind, the latter retaining the chief portion of the fusel oils. By repeated fractional distillation the spirit is obtained more and more concentrated, and separated from the still lower boiling admixtures ('first runnings'). The strongest rectified spirit still contains 5-10 % of water and some fusel oils. The first can be removed by chemical means, the latter by means of filtration through porous carbon.

As dehydrating agents, all energetically hygroscopic substances may be employed, especially such as do not combine with alcohole.g. ignited potassic carbonate, quick-lime, &c. Usually the strongest spirit is placed on quick-lime for 24 hours, with frequent shaking, then distilled from a water bath, and the distillate heated anew in similar manner. The last traces of water are removed by treatment with sodium, followed by distillation.

The smallest traces of water in alcohol may be detected by bringing it in contact with cupric sulphate, dried till colourless, when a blue colouration indicates the presence of water.

167. Absolute, i.e. entirely anhydrous and pure, ethylic alcohol is a colourless, mobile liquid of agreeable odour and burning taste, of sp. gr. 8063 at + 4° and 7895 at 20°. It boils under normal atmospheric pressure at 78.5°, and is still liquid at 90°. Easily inflamed, it burns with a bluish, feebly luminous flame. It is a strong poison.

Absolute alcohol possesses a very considerable affinity for water; it therefore dries damp substances energetically, and acts as an antiseptic. On mixing water with alcohol, heat is evolved, and contrac-tion, i.e. diminution of volume, takes place. This is most considerable when 52.3 volumes of alcohol are added to 47.7 volumes of water, the volume of the mixture being only 96.4. It appears as if a compound was formed of both in molecular quantities, as these proportions are sufficiently near to be represented by the formula C2H60,3H20. Alcohol more dilute than this does not apparently act as a drying agent.

In consequence of this diminution of volume, the alteration of the sp. gr. is not proportional to that of the mixture, though additions of water increase the density. By careful investigations, the sp. gr. of a large number of synthetically prepared mixtures of alcohol and water has been determined, and by means of tables so constructed the amount of alcohol in any aqueous solution may be ascertained by determining the density.

This can be done at once in liquids containing no foreign matters, but in cases where non-volatile matters are present, as in most alcoholic drinks, this method can no longer be directly applied, and the following is substituted :-A given volume of the solution to be tested is submitted to distillation, the first distillates, which contain all the alcohol, made up to the original volume with water, and the gravity then determined. The gravity is most quickly determined by a hydrometer, whose scale, instead of sp. gr., gives the corresponding amount of alcohol, either in % by volume (Tralle's alcoholometer) or in % by weight (Richter's alcoholometer).

The general relations between the mixed contents, by volume or by weight, and the sp. gr. is sufficiently shown by the following table: