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Crude montanic acid was extracted from montan wax by the following process: 500 grams of montan wax were digested five times with hot alcohol, about 3 litres for each extraction. This hot alcoholic solution, containing practically the whole of the free acids, was siphoned off, neutralized with ammonia, and the acids were then precipitated as calcium salts by means of alcoholic calcium-chloride solution. The calcium salts were then filtered off by means of a hot funnel.
The crude calcium salts thus obtained were dried on the water bath, and then pulverized and boiled out six times with alcohol. Motor spirit, although a very good solvent of unsaponifiable matter, could not be employed for the purification of the calcium salts, by reason of the almost unfiltrable paste produced in this case.
The calcium salts were now decomposed by glacial acetic acid, and the crude acid thus obtained melted at 81°5°. Crystallization from motor spirit raised the melting-point to 82°5°, but further crystallization from alcohol, motor spirit, and acetic acid did not further raise the melting-point. The acid crystallized from acetic acid in granules.
The titration of the acid thus obtained, although the greatest care was taken in the standardization of the decinormal solutions employed, gave a molecular weight of 432—i.e., almost the mean of the molecular weights required for the formulae C29H58O2 and C28H56O2.
It thus appeared that either the montanic acid contained some inert compounds such as hydrocarbons or ketones, or that it was admixed with a higher acid. To test the first of these suppositions the acid was purified by potash-lime saponification with an excess of lime, and then extraction with hot motor spirit in which high-molecular-weight hydrocarbons and ketones are readily soluble. The molecular weight of the purified acid, however, remained unchanged (430).
That the acid, although its melting-point was unaltered by further crystallization, was not a single compound was demonstrated by submitting 10 grams of the acid to fractional precipitation with magnesium acetate, for the regenerated acids from the different fractions had the following melting-points:—
| Melting-point. | |||
|---|---|---|---|
| Fraction | I | (weight 1/10 of original acid taken) | 85°5° |
| " | II | " 3/10 " | 83–84° |
| " | III | " 4/10 " | 81–82° |
| " | IV | " 1/10 " | 74°5° |
Fractional precipitation was therefore undertaken on a large scale. 50 grams of crude montanic acid were dissolved in 800 c.c. of alcohol, the solution rendered alkaline with ammonia, and then precipitated with 20 c.c. of a solution of magnesium acetate (equivalent to 10 grams montanic acid). Four fractions were thus precipitated, and a fifth fraction was obtained from the alcoholic filtrate on cooling. The regenerated acids from these fractions had the following melting-points:—
| Melting-point. | |
|---|---|
| Fraction 1 | 83°5–84° |
| " 2 | 83–84° |
| " 3 | 82–83° |
| " 4 | 81–82° |
| " 5 | 74–76° |
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This practically agrees with Eisenreich's experience. He obtained the first four fractions melting at 83°. It seems strange that he did not proceed with further fractional precipitation.
Fractions 1 and 2 were each fractionally precipitated again, and it was found that the regenerated acids from the first two precipitates had risen 3° in melting-point.
Fractions which melted within 1° were mixed before the next precipitation was proceeded with. After four consecutive precipitations of the highest melting fraction in each case, there resulted an acid melting at 88°5°. This fraction was not altered in melting-point by a series of further fractional precipitations, and must be regarded as pure melissic acid, which, according to Brodie* and to Schwalb,† melts at 88–89°. It is, however, to be noted that the melissic acid from the oxidation of canaüba wax is stated by Maskelyne‡ to melt at 91°.
The following is a scheme of precipitations employed in the isolation of melissic acid. The melting-points given are those of the regenerated acids:—
Repeated fractional precipitation failed to yield an acid melting at about 83° which could be considered pure, but from fraction 5 precipitation yielded lower fractions, which when repeatedly crystallized melted at
[Footnote] * Phil. Trans. Roy Soc, 1848.
[Footnote] † Annalen, 235, p. 135.
[Footnote] ‡ Journ. Chem. Soc., 1869, vol. 22, p. 87.
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78–78°5°, and were absolutely identical with the cerotic acid of beeswax. This identity was proved as follows:—
(a.) Both acids had the same melting-point, and a mixture of the two acids melted within 0°5° of the original acid.
(b.) The ketone prepared from each, by means of the catalytic action of metallic iron, melted at 92°5–93°.
(c.) The ethyl esters of each acid had the same boiling-point, 285°, at 14 mm.
(d.) Both acids crystallized in pearly scales.