_Canada snake root oil_, from the root of Asarum canadense. Specific gravity at 15 C., 0.940-0.962; optical rotation, slightly laevo-rotatory up to -4; refractive index at 20 C., 1.485-1.490; saponification number, 100-115; soluble in 3 or 4 volumes of 70 per cent. alcohol.

The princ.i.p.al const.i.tuents of the oil are a terpene, asarol alcohol, another alcohol, and methyl eugenol. The oil is too expensive to be used in other than high-cla.s.s toilet soaps.

_Cananga_ or _Kananga oil_, the earlier distillate from the flowers of Cananga odorata, obtained chiefly from the Philippine Islands. Specific gravity at 15 C., 0.910-0.940; optical rotation, -17 to -30; refractive index at 20 C., 1.4994-1.5024; esters, calculated as linalyl benzoate, 8-15 per cent.; soluble in 1.5 to 2 volumes of 95 per cent.

alcohol, but becoming turbid on further addition.

The oil is qualitatively similar in composition to Ylang-Ylang oil, and contains linalyl benzoate and acetate, esters of geraniol, cadinene, and methyl ester of p-cresol.

_Caraway oil_, distilled from the seeds of Carum carui. Specific gravity at 15 C., 0.907-0.915; optical rotation, +77 to +79; refractive index at 20 C., 1.485-1.486; soluble in 3 to 8 volumes of 80 per cent.

alcohol. The oil should contain 50-60 per cent. of carvone, which is estimated by absorption with a saturated solution of neutral sodium sulphite. The remainder of the oil consists chiefly of limonene.

_Ca.s.sia oil_, distilled from the leaves of Cinnamomum ca.s.sia, and shipped to this country from China in lead receptacles. Specific gravity at 15 C., 1.060-1.068; optical rotation, slightly dextro-rotatory up to +3 30'; refractive index at 20 C., 1.6014-1.6048; soluble in 3 volumes of 70 per cent. alcohol as a general rule, but occasionally requires 1 to 2 volumes of 80 per cent. alcohol.

The value of the oil depends upon its aldehyde content, the chief const.i.tuent being cinnamic aldehyde. This is determined by absorption with a hot saturated solution of sodium bisulphite. Three grades are usually offered, the best containing 80-85 per cent. aldehydes, the second quality, 75-80 per cent., and the lowest grade, 70-75 per cent.

Other const.i.tuents of the oil are cinnamyl acetate and cinnamic acid.

This oil gives the characteristic odour to Brown Windsor soap, and is useful for sweetening coal-tar medicated soaps.

_Cedarwood oil_, distilled from the wood of Juniperus virginiana.

Specific gravity at 15 C., 0.938-0.960; optical rotation, -35 to -45; refractive index at 20 C., 1.5013-1.5030. The princ.i.p.al const.i.tuents are cedrene and cedrol.

_Cinnamon oil_, distilled from the bark of Cinnamomum zeylanic.u.m.

Specific gravity at 15 C., 1.00-1.035; optical rotation, laevo-rotatory up to -2; usually soluble in 2 to 3 volumes of 70 per cent. alcohol, but sometimes requires 1 volume of 80 per cent. alcohol for solution; aldehydes, by absorption with sodium bisulphite solution, 55-75 per cent.; and phenols, as measured by absorption with 5 per cent. potash, not exceeding 12 per cent.

The value of this oil is not determined entirely by its aldehyde content as is the case with ca.s.sia oil, and any oil containing more than 75 per cent. aldehydes must be regarded with suspicion, being probably admixed with either ca.s.sia oil or artificial cinnamic aldehyde. The addition of cinnamon leaf oil which has a specific gravity at 15 C. of 1.044-1.065 is detected by causing a material rise in the proportion of phenols.

Besides cinnamic aldehyde the oil contains eugenol and ph.e.l.landrene.

_Citronella Oil._--This oil is distilled from two distinct Andropogon gra.s.ses, the Lana Batu and the Maha pangiri, the former being the source of the bulk of Ceylon oil, and the latter being cultivated in the Straits Settlements and Java. The oils from these three localities show well-defined chemical differences.

_Ceylon Citronella oil_ has the specific gravity at 15 C., 0.900-0.920; optical rotation, laevo-rotatory up to -12; refractive index at 20 C., 1.480-1.484; soluble in 1 volume of 80 per cent. alcohol; total acetylisable const.i.tuents, calculated as geraniol, 54-70 per cent.

_Singapore Citronella Oil._--Specific gravity at 15 C., 0.890-0.899; optical rotation, usually slightly laevo-rotatory up to -3; refractive index at 20 C., 1.467-1.471; soluble in 1 to 1.5 volumes of 80 per cent. alcohol; total acetylisable const.i.tuents, calculated as geraniol, 80-90 per cent.

_Java Citronella Oil._--Specific gravity at 15 C., 0.890-0.901; optical rotation, -1 to -6; total acetylisable const.i.tuents, calculated as geraniol, 75-90 per cent.; soluble in 1-2 volumes of 80 per cent.

alcohol.

The chief const.i.tuents of the oil are geraniol, citronellal, linalol, borneol, methyl eugenol, camphene, limonene, and dipentene. It is very largely used for perfuming cheap soaps, and also serves as a source for the production of geraniol.

_Bois de Rose Femelle oil_, or _Cayenne linaloe oil_, distilled from wood of trees of the Burseraceae species. Specific gravity at 15 C., 0.874-0.880; optical rotation, -11 30' to -16; refractive index at 20 C., 1.4608-1.4630; soluble in 1.5 to 2 volumes of 70 per cent. alcohol.

The oil consists almost entirely of linalol, with traces of saponifiable bodies, but appears to be free from methyl heptenone, found by Barbier and Bouveault in Mexican linaloe oil. This oil is distinctly finer in odour than the Mexican product.

_Clove oil_, distilled from the unripe blossoms of Eugenia caryophyllata, the chief source of which is East Africa (Zanzibar and Pemba). Specific gravity at 15 C., 1.045-1.061; optical rotation, slightly laevo-rotatory up to -1 30'; phenols, estimated by absorption with 5 per cent. potash solution, 86-92 per cent.; refractive index at 20 C., 1.5300-1.5360; soluble in 1 to 2 volumes of 70 per cent.

alcohol.

The princ.i.p.al const.i.tuent of the oil is eugenol, together with caryophyllene and acet-eugenol. While within certain limits the value of this oil is determined by its eugenol content, oils containing more than 93 per cent. phenols are usually less satisfactory in odour, the high proportion of phenols being obtained at the expense of the decomposition of some of the sesquiterpene. Oils with less than 88 per cent. phenols will be found somewhat weak in odour. This oil is extensively used in the cheaper toilet soaps and is an important const.i.tuent of carnation soaps. As already mentioned, however, it causes the soap to darken in colour somewhat rapidly, and must not therefore be used in any quant.i.ty, except in coloured soaps.

_Concrete orris oil_, a waxy substance obtained by steam distillation of Florentine orris root.

Melting point, 35-45 C., usually 40-45 C.; free acidity, calculated as myristic acid, 50-80 per cent.; ester, calculated as combined myristic acid, 4-10 per cent.

The greater part of the product consists of the inodorous myristic acid, the chief odour-bearing const.i.tuent being irone. The high price of the oil renders its use only possible in the very best quality soaps.

_Eucalyptus Oil._--Though there are some hundred or more different oils belonging to this cla.s.s, only two are of much importance to the soap-maker. These are:--

(i.) Eucalyptus citriodora. Specific gravity at 15 C., 0.870-0.905; optical rotation, slightly dextro-rotatory up to +2; soluble in 4-5 volumes of 70 per cent. alcohol.

The oil consists almost entirely of citronellic aldehyde, and on absorption with saturated solution of sodium bisulphite should leave very little oil unabsorbed.

(ii.) Eucalyptus globulus, the oil used in pharmacy, and containing 50-65 per cent. cineol. Specific gravity at 15 C., 0.910-0.930; optical rotation, +1 to +10; soluble in 2 to 3 parts of 70 per cent. alcohol; cineol (estimated by combination with phosphoric acid, pressing, decomposing with hot water, and measuring the liberated cineol), not less than 50 per cent. Besides cineol, the oil contains d-pinene, and valeric, butyric, and caproic aldehydes. It is chiefly used in medicated soaps.

_Fennel (sweet) oil_, obtained from the fruit of Foeniculum vulgare, grown in Germany, Roumania, and other parts of Europe. Specific gravity at 15 C., 0.965-0.985; optical rotation, +6 to +25; refractive index at 20 C., 1.515-1.548; usually soluble in 2-6 parts 80 per cent.

alcohol, but occasionally requires 1 part of 90 per cent. alcohol.

The chief const.i.tuents of the oil are anethol, fenchone, d-pinene, and dipentene.

_Geranium oils_, distilled from plants of the Pelargonium species.

There are three princ.i.p.al kinds of this oil on the market--the African, obtained from Algeria and the neighbourhood, the Bourbon, distilled princ.i.p.ally in the Island of Reunion, and the Spanish. The oil is also distilled from plants grown in the South of France, but this oil is not much used by soap-makers. A specially fine article is sold by a few essential oil firms under the name of "Geranium-sur-Rose," which as its name implies, is supposed to be geranium oil distilled over roses. This is particularly suitable for use in high-cla.s.s soaps. The following are the general properties of these oils. It will be seen that the limits for the figures overlap to a considerable extent.

_________________________________________________________________________ | | | | | | | | African. | Bourbon. | Spanish. | French. | |_________________________|___________|___________|___________|___________| | | | | | | | Specific gravity | | | | | | at 15 C. | .890-.900 | .888-.895 | .895-.898 | .897-.900 | | Optical rotation. |-6 to -10|-9 to -18|-8 to -11|-8 to -11| | Esters, calculated as | 20-27 | 27-32 | 20-27 | 18-23 | | geranyl tiglate | per cent. | per cent. | per cent. | per cent. | | Total alcohols, as | 68-75 | 70-80 | 65-75 | 66-75 | | geraniol. | per cent. | per cent. | per cent. | per cent. | | Solubility in 70 per | | | | | | cent. alcohol. | 1 in 1.5-2| 1 in 1.5-2| 1 in 2-3 | 1 in 1.5-2| |_________________________|___________|___________|___________|___________|

The oil contains geraniol and citronellol, both free, and combined with tiglic, valeric, butyric, and acetic acids; also l-menthone. The African and Bourbon varieties are the two most commonly used for soap-perfurmery, the Spanish oil being too costly for extensive use.

_Ginger-gra.s.s oil_, formerly regarded as an inferior kind of palma-rosa but now stated to be from an entirely different source. Specific gravity at 15 C., 0.889-0.897; optical rotation, +15.

The oil contains a large amount of geraniol, together with di-hydroc.u.min alcohol, d-ph.e.l.landrene, d-limonene, dipentene, and l-carvone.

_Guaiac wood oil_, distilled from the wood of Bulnesia sarmienti.

Specific gravity at 30 C., 0.967-0.975; optical rotation, -4 30' to -7; refractive index at 20 C., 1.506-1.507; soluble in 3 to 5 volumes of 70 per cent. alcohol.

The princ.i.p.al const.i.tuent of the oil is guaiac alcohol, or gusiol. This oil, which has what is generally termed a "tea-rose odour," is occasionally used as an adulterant for otto of rose.

_Lavender oil_, distilled from the flowers of Lavandula vera, grown in England, France, Italy and Spain. The English oil is considerably the most expensive, and is seldom, if ever, used in soap. The French and Italian oils are the most common, the Spanish oil being a comparatively new article, of doubtful botanical origin, and more closely resembling aspic oil.

English Oil.--Specific gravity at 15 C., 0.883-0.900; optical rotation, -4 to -10; esters, calculated as linalyl acetate, 5-10 per cent.; soluble in 3 volumes of 70 per cent. alcohol.

French and Italian Oils.--Specific gravity at 15 C., 0.885-0.900; optical rotation, -2 to -9; refractive index at 20 C., 1.459-1.464; esters, calculated as linalyl acetate, 20-40 per cent., occasionally higher; soluble in 1.5-3 volumes of 70 per cent. alcohol.

There was at one time a theory that the higher the proportion of ester the better the oil, but this theory has now to a very large extent become discredited, and there is no doubt that some of the finest oils contain less than 30 per cent. of esters.

Spanish Oil.--Specific gravity at 15 C., 0.900-0.915; optical rotation, -2 to +7; esters, calculated as linalyl acetate, 2-6 per cent.; soluble in 1-2 volumes of 70 per cent. alcohol.

The chief const.i.tuents of lavender oil are linalyl acetate, linalol, geraniol, and linalyl butyrate, while the English oil also contains a distinct amount of cineol.

_Lemon oil_, prepared by expressing the peel of the nearly ripe fruit of Citrus limonum, and obtained almost entirely from Sicily and Southern Italy. Specific gravity at 15 C., 0.856-0.860; optical rotation, +58 to +63; refractive index at 20 C., 1.4730-1.4750; aldehydes (citral), 2.5 to 4 per cent.

The princ.i.p.al const.i.tuents of the oil are limonene and citral, together with small quant.i.ties of pinene, ph.e.l.landrene, octyl and nonyl aldehydes, citronellal, geraniol, geranyl acetate, and the stearopten, citraptene.