Pharmacopedia, a commentary on the British pharmacopoeia, 1898 / by Edmund White ... and John Humphrey.

  • White, Edmund.
Date:
1901
Catalogue details

Licence: In copyright

Credit: Pharmacopedia, a commentary on the British pharmacopoeia, 1898 / by Edmund White ... and John Humphrey. Source: Wellcome Collection.

Provider: This material has been provided by King’s College London. The original may be consulted at King’s College London.

    47/724 (page 23)
    of any desired organism and so obtain chiefly the products characteristic of the fermentative activity of this organism. For the development of the BaciUus acidi lactici the most favourable conditions are (i) temperature about 35 C. ; (2) neutral or faintly alkaline solution ; (3) presence of proteids (albuminous sub- tances). To obtain lactic acid from sugar, decayed cheese is added ; this consists chiefly of casein (proteids) and contains abundance of the lactic acid bacilli. Chalk or zinc oxide is also added to neutralise the acid as fast as it is produced (since the activity of the lactic ferment is diminished by the presence of free acid), and the mixture is set aside and frequently stirred for about a week, at a temperature of 35°-40° C. It is then boiled, filtered, and the filtrate evaporated to crystallise out ^ the zinc or calcium lactate. From the solution of the calcium salt the acid is obtained by the addition of the required quantity of sulphuric acid, and from the zinc salt by precipitating the zinc as sulphide, with hydrogen sulphide. After removing the calcium sulphate or zinc sulphide by filtration, the filtrate is evaporated on the water bath. If the fermentation mixture be allowed to become acid, or to stand too long, then butyric fermentation sets in, by which the lactic is converted into butyric acid, hydrogen being evolved. Milk sugar is officially specified as the source of lactic acid, but glucose or invert sugar is also used for the purpose. The empirical formula for lactic acid, CaHoOg, is exactly half that of glucose, CeHpOo; but it is not known how the bacillus effects the , . ^ CH3-CH(0H)-C00H, conversion of the sugar to lactic acid. Lactic acid, ^ a is also known as a-hydroxy-propionic acid, since it is derived from propionic acid by substitution of hydroxyl for hydrogen combined with the carbon atom nearest the carboxyl group. This nomenclature is adopted in order to distinguish isomeric substances, the successive atoms in the carbon chain being distinguished by the Greek letters 7, proceeding from the end next to the characteristic group of the mother substance. Thus CH2(OH)-CH2-COOH is iS-hydroxy-propionic acid, otherwise known as hydracrylic acid. Inspection of the formula for lactic acid shows that it contains one asymmetric carbon atom—i.e., a carbon atom combined with four different groups or elements : in this case CHg, H, OH, and COOH, thus— H CHa—C—COOH. oL: It can, therefore, exist in three stereo-isomeric forms: (i) dextro-rotatory, (2) laevo- rotatory, and (3) racemic or inactive. The last is produced by mixing equal proportions of the dextro- and Igevo-varieties, and is the kind obtained in the fermentation of lactose by means of putrid cheese. Dextro-lactic acid occurs in flesh, and is known as para- or sarco-lactic acid, while laevo-lactic acid has been obtained by the fermentative activity of a special organism on sugar solutions. All three can also be produced by synthetical processes. Characters and Tests.—Lactic acid is a colourless, syrupy, hygroscopic liquid, without odour, but with a sour taste, and acid reaction. It is miscible