The practical methods of organic chemistry / by Ludwig Gattermann ; translated by William B. Schober.

  • Ludwig Gattermann
Date:
1901
Catalogue details

Licence: In copyright

Credit: The practical methods of organic chemistry / by Ludwig Gattermann ; translated by William B. Schober. Source: Wellcome Collection.

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    they do not separate from their solutions on mere cooling. In this case, in order to obtain crystals, a portion of the sol- vent must be allowed to evaporate. (Crystallisation by Evapo- ration. ) Solvents. — As solvents for organic compounds, the following substances are principally used : Class I. Water, Alcohol, Ether, Ligroi'n (Petroleum Ether), Glacial Acetic Acid, Less frequently used than these are : hydrochloric acid, carbon disulphide, acetone, chloroform, ethyl acetate, methyl alcohol, amyl alcohol, toluene, xylene, solvent naphtha, etc. But rarely used are: pyridine, naphthalene, phenol, nitro- benzene, aniline, and others. Choice of the Solvent. — The choice of a suitable solvent is often of great influence upon the success of an experiment, in that a solid compound does not assume a completely characteristic appearance until it is uniformly crystallised. In order to find the most appropriate solvent, preliminary experiments are made in the following manner: successive small portions of the finely pulverised substance (a few milligrammes will suffice) are treated in small test-tubes, with small quantities of the solvents of Class I. If solution takes place at the ordinary temperature, or on gentle heating, the solvent in question is, provisionally, left out of con- sideration. The remaining portions are heated to boiling, until, after the addition of more of the solvent if necessary, solution Benzene. Also mixtures of these : Class II. Water 4-Alcohol, Water -f Glacial Acetic Acid, Ether + Ligroi’n, Benzene + Ligroi'n.
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