CITRAL AND ITS ANALYSIS IN TERPENELESS EXTRACT OF

LEMON.

By SAMUEL H. BAER.

The analyses were made by three chemists, including the writer, and as all three judged the colors, it would seem that the analyses are as accurate as the colorimetric method permits. Acknowledgment is due S. E. Shaffner for assistance rendered.

Determination of citral in lemon extract by the colorimetric method.

10 Terpeneless oil of lemon solution (dissolved in cologne spirits, 190 proof, or 95 per cent, and colored with lemon peel).

11

Terpeneless oil of lemon solution (dissolved in cologne spirits, 190 proof, or
95 per cent, and colored with turmeric)..

12 Terpeneless oil of lemon solution (dissolved in 38 per cent cologne spirits
and city water and filtered through magnesia).

Citral solution (dissolved in cologne spirits of 190 proof, or 95 per cent)..
17 pounds oil of lemon, 19 gallons cologne spirits, 23 gallons water (col-
ored with lemon peel and filtered through magnesia)..

15 Alcohol (not cologne spirits, 188 proof, generally used by manufacturers).
Cologne spirits, 190 proof...

17

50 per cent cologne spirits with city water.

18

50 per cent cologne spirits filtered through magnesia....

From these analyses it is seen that when the colorimetric method is applied to the extracts of commerce, the correct result is not obtained. On sample No. 13, a citral solution, the analysis was reasonably close; samples No. 10 and 11 are terpeneless oils of lemon and the low results on citral may be due to the fact that the sample purchased was not pure terpeneless oil of lemon, but a product containing only 50 per cent of the citral that should be there.

Most of the extract manufacturers use 188 proof alcohol, that is, 94 per cent alcohol, which always contains a certain amount of aldehydes, and the sample used in this test, treating the alcohol the same as the lemon extract, showed 0.19 per cent of citral, when there was no citral there at all. If only cologne spirits are used, the results obtained are not so far wrong as if 94 per cent alcohol is used.

Since, therefore, the presence of the impurities in alcohol throw the results off to such an extent, giving too high a per cent of citral, would it not be possible that the impurities in the alcohol at certain times and also in the water, and the very change of one or two ingredients in the lemon oil, might make the result inaccurate, reversing the analysis and showing a smaller per cent of citral than is really present?

The colorimetric method is applicable if the manufacturer used chemically pure citral, distilled water, and aldehyde-free alcohol in the manufacture of his extracts, but such ideal conditions never exist. Further, any manufacturer could discreetly add another aldehyde, even acetaldehyde, to the extent of 0.2 per cent, which would give all the reactions of citral in the extract of lemon by the colorimetric method.

The method is not without use, but if the presence of citral could be determined and estimated quantitatively by a sodium sulphite or carbazone method, then the colorimetric method might be used as a check. Before adopting the colorimetric method as official a committee should be appointed from the association members to test it carefully, under the conditions that the manufacturer must meet since he can not use aldehyde-free alcohol, nor is he always in a position to use distilled water.

Further, suppose the method is accurate, how would the analyses show that the citral used was obtained from lemon oil or the commercial citral obtained from lemon grass oil?

AN OUTLINE TO ASSIST IN THE IDENTIFICATION OF CERTAIN WATER-SOLUBLE COAL-TAR COLORS.

By C. B. COCHRAN.

The reactions given by the coal-tar colors listed in the following outline were all obtained with solutions as dilute as they could be made and still give reactions sufficiently clear and definite to furnish a basis for positive conclusions. Because of the degree of dilution the results here tabulated will, in some cases, appear contradictory to those given by Schultz and Julius. For example, these authors may report a color precipitated by a certain reagent when the precipitation is only partial and therefore does not appear in dilute solutions such as have been used in the preparation of these tables.

The sodium bisulphite reagent is prepared by saturating a 5 per cent solution of sodium hydroxid with sulphur dioxid. The absorption tests with aluminum hydroxid were made by adding between 2 and 3 cc of well-washed aluminum hydroxid (from which the excess of water has been drained through the filter) to 10 cc of the color solution.

The tests with the fuller's earth were made by adding 2 cc of the earth to 10 ce of the color solution. In these absorption tests the aluminum hydroxid and fuller's earth are shaken with the color solution. If, after setting, the supernatant liquid is colorless or very nearly so, the result is recorded as color absorbed. In the majority of cases the results obtained with aluminum hydroxid and fuller's earth are definite and sharp. There are many colors belonging to Class I (Rota's classification) which are much more readily absorbed from their water solutions by aluminum hydroxid than by fuller's earth, while the reverse is true of many colors belonging to Classes II, III, and IV.

In the dyeing tests sodium carbonate was used for making alkaline and hydrochloric acid for acidifying. The alkali solution was very weak and the acid bath about onehalf the official strength (1 cc strong hydrochloric acid to 50 cc).

The numbers following the names of the colors refer to the 1904 edition of Green's tables.

COAL-TAR COLORS OF CLASS I.

Solution reduced and in most cases decolorized by stannous chlorid. Original color not restored by hydrogen dioxid.

DIVISION I.-COLOR ABSORBED BY ALUMINUM HYDROXID.

Dye wool red.

SECTION I.-Color precipitated by sodium bisulphite reagent.

Congo red (A) (240) dyes wool and unmordanted cotton red from neutral or faintly alkaline bath, but not from acid bath. Oxalic acid or acetic acid gives a blue precipitate and colorless filtrate.

SECTION II. Color not precipitated nor solution changed by sodium bisulphite reagent.

Fast red A (102), hydrochloric acid gives a brown precipitate and colorless filtrate. Dyes wool and unmordanted cotton red from acid, alkaline, or neutral bath. Color precipitated by barium chlorid solution.

Azo rubin S (103), color only partially precipitated by hydrocholoric acid. Dyes wool red from acid bath but not from alkaline bath. Does not readily dye unmordanted cotton in either bath. Color not precipitated by barium chlorid.

Dyes wool yellow.

Chrysamin R (269), hydrochloric acid gives a brown precipitate, sodium hydroxid a red solution. Barium chlorid and sodium bisulphite reagent each gives a yellow precipitate and colorless filtrate. Dyes wool pale yellow from a neutral bath and unmordanted cotton orange yellow from a neutral or alkaline bath.

Dye wool and unmordanted cotton brown from acid bath.

Bismarck brown (197), decolorized by stannous chlorid and on adding hydrogen dioxid a color somewhat redder than the original color appears. Color precipitated by tannin reagent. Color absorbed from alkaline solution by ether, and on adding dilute acetic acid to the ether solution, the color is taken up by the acid.

Resorcin brown (137), decolorized by stannous chlorid. No color returns on adding hydrogen dioxid. Not precipitated by tannin reagent. Color absorbed by fuller's earth.

DIVISION II.-COLOR NOT ABSORBED OR ONLY PARTIALLY ABSORBED BY ALUMINUM HYDROXID.

Dye wool red in acid bath.

SECTION I.-Sodium hydroxid causes a distinct change in color of water solution. (1) Sodium hydroxid turns water solution violet.

Ponceau 6 R. B. (169), dyed wool is bluish red, turned blue by hydrochloric acid or sulphuric acid, color in wool dissolves in either acid, giving a blue solution. Hydrochloric acid turns water solution violet, more turns it blue.

(2) Sodium hydroxid turns water solution brown.

Brilliant crocein (146), hydrochloric acid produces little change in color of water solution.

Crystal ponceau (A) (64), dyed wool turned violet by hydrochloric acid and blue by sulphuric acid.

Crocein scarlet 3 B X (104), dyed wool turned red violet by hydrochloric acid or by sulphuric acid.

New coccin (A) (106), color of dyed wool not changed by hydrochloric acid. (3) Sodium hydroxid turns water solution yellow.

Palatin scarlet (53), dyed wool is scarlet. Color not much changed by hydrochloric acid, but sulphuric acid turns it violet and gives a violet solution. On dilution wool has nearly original color.

SECTION II.-Sodium hydroxid does not cause a distinct change in the color of the water solution.

Group I.-Sulphuric acid turns dyed wool blue or violet and gives a blue or violet solution. Dyed wool is bluish red.

Bordeaux B (A) (65), hydrochloric acid turns dyed wool violet.

Bordeaux S (A) (107), scarlet B. E. E. (P) closely related to Bordeaux S.

Group II-Sulphuric acid has little or no effect on color of dyed wool. Dyed wool is scarlet.

Ponceau G (A) (55), barium chlorid gives an orange red precipitate, wool dyed orange red.

Ponceau 3 R (A) (56), barium chlorid gives a red precipitate. Dyes wool more red than (55).

Dye wool yellow or orange.

SECTION I.-Hydrochloric acid added to strong acidification precipitates the color or decolorizes the solution (the nitro colors).

Group I.-Color extracted by ether from solution acidified with hydrochloric acid. Victoria yellow (2).

Martius yellow (3), water solution plus potassium cyanid gives a brown color on warming.

Group II.-Color not extracted by ether from solution acidified with hydrochloric acid.

Naphthol yellow S (4).

SECTION II.-Hydrochloric acid causes a decided change in the color of the water solution (many of the tropaolins).

Group I.-Hydrochloric acid turns dyed wool violet.

Dyed wool is yellow.

Brilliant yellow S (Sch.) (89), dyed wool is yellow turned violet by hydrochloric acid.

Metanil yellow (Sch.) (95), dyed wool is orange yellow turned violet by hydrochloric acid.

Group II-Hydrochloric acid turns dyed wool brown.

Chrysoidin R (18). This color is absorbed by fuller's earth and partially absorbed by aluminum hydroxid.

Group III.-Hydrochloric acid turns dyed wool red.

Fast yellow (8).

SECTION III.-Color of water solution not decidedly changed by hydrochloric acid. (If a precipitate appears only a part of the color is precipitated.)

Dyed wool is yellow.

Naphthol yellow S (4), dyed wool is decolorized by hydrochloric acid.

Tartrazin (94), color of dyed wool not changed by hydrochloric acid.

Dyed wool is yellow orange to orange.

Tropoolin O (84).

Tropoolin 000 (85).

Orange G (14).

Dyed wool is red orange.

Mandarin G (86), dyed wool is turned red violet by hydrochloric acid or sulphuric acid.

Ponceau 4 G. B., color of dyed wool not changed by hydrochloric acid nor by sulphuric acid.

COLORS OF CLASS II.

Solution decolorized by stannous chlorid, original color returns on addition of hydrogen dioxid. (Bismarck brown, which might be referred to this class, is included under Class I.)

(1) Dyes wool and cotton bluish red (most readily from an alkaline bath). Safranin (584), much hydrochloric acid turns water solution blue violet. Color absorbed by fuller's earth, precipitated by tannin reagent. Sulphuric acid turns dyed wool green, solution green, hydrochloric acid blue.

(2) Dyes wool blue from alkaline or neutral bath, cotton a paler blue from neutral bath.

Methylene blue (650), color absorbed by fuller's earth precipitated by tannin; hydrochloric acid turns dyed wool robin's-egg blue, sulphuric acid green.

COLORS OF CLASS III.

Stannous chlorid produces no further effect on the color than hydrochloric acid. Sodium hydroxid produces a precipitate or decolorizes the solution. All the colors given in this class except auramin (425) are decolorized by sodium bisulphite reagent.

The color reappears on heating and disappears on cooling. With the exception of acid magenta (A) (462) they are all absorbed by fuller's earth.

Dye wool red.

(1) Dye wool from acid bath only, do not dye unmordanted cotton in either bath. Acid magenta (462), color absorbed by aluminum hydroxid. Dyed wool is decolorized by hydrochloric acid, sulphuric acid, sodium hydroxid, or ammonium hydroxid. Tannin reagent gives no precipitate.

(2) Dyes wool and also unmordanted cotton most readily from a neutral bath.

Fuchsin (448), color not absorbed by aluminum hydroxid. Dyed wool turned red brown by hydrochloric acid or sulphuric acid. Tannin reagent gives a precipitate. (3) Dyes wool yellow from neutral or alkaline bath. Does not dye unmordanted cotton. Auranin (425).

Dye wool green.

Dye from acid bath: Guinea green B (A) (433) and acid green (434) do not dye cotton. Dye from neutral or alkaline bath: Ethyl green (428) dyes unmordanted cotton more readily than malachite green.

Malachite green (427), dyed wool is blue green, turned at first grass green by hydrochloric acid or sulphuric acid, then yellow; on dilution, blue.

Dye wool violet from neutral or alkaline bath.

Methyl violet (451), sodium hydroxid gives a brown precipitate and brown solution. Ethyl violet (453), sodium hydroxid gives a white precipitate, colorless on warming. Either dyes unmordanted cotton from alkaline bath.

Dyes wool blue from acid bath.

China blue (480), color absorbed by aluminum hydroxid. Solution decolorized by sodium bisulphite reagent. Color does not readily return on heating, but does return on adding a drop of hydrochloric acid. Dyed wool decolorized by ammonium hydroxid, turned reddish brown by sulphuric acid.

COLORS OF CLASS IV.

Colors not reduced by stannous chlorid. Solution not decolorized and color not completely precipitated by sodium hydroxid.

Dye wool red from neutral bath.

Dyed wool is red orange to orange red:

Eosin (512), color not absorbed by fuller's earth nor by aluminum hydroxid. Water solution yellow to orange with green fluorescence. Hydrochloric acid or sodium bisulphite reagent gives an orange precipitate.

Dye wool bluish red from neutral bath:

(a) Color completely absorbed by fuller's earth. Sodium bisulphite reagent gives no precipitate, but causes only a loss of fluorescence.

Rhodamin G (502), water solution red violet with red fluorescence.

Rhodamin B (504), water solution bluish red with orange brown fluorescence. (b) Color only partially absorbed by fuller's earth. Sodium bisulphite reagent precipitates the color.

Erythrosin (516), water solution cherry red. (Green's tables give no fluorescence. A sample marked "Grübler" gave green fluorescence.) Hydrochloric acid gives an orange brown precipitate. Sodium bisulphite reagent gives an orange-red precipitate. Rose bengal (520), water solution cherry red. No fluorescence. Hydrochloric acid gives a brown-red precipitate. Sodium bisulphite reagent a pink precipitate. Phloxin (521), water solution bluish red with green fluorescence. Hydrochloric acid gives an orange precipitate. Sodium bisulphite a pink precipitate.