CamwoodCHAPTER XVIII. Colouring Matters of Unknown Constitution. The Insoluble Red Woods

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Camwood or "cambe wood," stated to be derived from a variety of Baphia nitida (cf. barwood), is very similar in general properties to the "insoluble red" dyewoods already described. It is, however, more expensive, yields deeper shades on dyeing, and its colouring matter is said to be more soluble than that present in the other woods.

It has been recently examined by O'Neill and Perkin (Chem. Soc. Trans.,1918, 113, 126), who employed for this purpose similar methods to those found serviceable with sanderswood (loc. cit.).

Iso-santalin, the main colouring matter, forms a chocolatecoloured powder, which on grinding becomes redder in appearance, and is readily soluble in boiling methylated spirit. When heated, it shows no sign of melting, darkens at 280°, and is fully decomposed at 290-300°, being then a carbonaceous powder. It possesses the formula C₂₂H₁₆O₆(OCH₃)₂, gives with alcoholic potassium acetate the salt C₉₆H₈₃O₂₂K or C₇₂H₆₅O₂₄K, shows evidence of the formation of soluble oxonium salts, and in general properties closely resembles its isomer santalin. The colour reactions and also the dyeing properties of the two compounds indicate, however, that they are distinct substances:

Alcoholic hydrobromic acid
Santalin - Crimson
Iso-santalin - Reddish-violet

Dilute sodium hydroxide
Santalin - Dull red
Iso-santalin - Dull violet

Alcoholic ferric chloride
Santalin - Violet
Iso-santalin - Bluish-violet

For dyeing the colouring matter in alcoholic solution was added to the water in the dye-bath and the dyeings were carried out (a) employing wool alone, (b) employing wool alone and subsequently saddening with bichrome, (c) employing wool mordanted with bichrome and cream of tartar, and (d) employing wool mordanted with bichrome and sulphuric acid.

Santalin
(a) Pale dull red.
(b) Dull reddish-brown
(c) Pale reddish-pink
(d) Pale red-pink

Iso-santalin
(a) Pale violet-red
(b) Dull violet-maroon
(c) Violet-red
(d) Violet-red weaker than (c)

Acetyl-iso-santalin, C₂₄H₁₈O₈(C₂H₃O)₄, consists of a deep salmoncoloured powder, and does not possess a definite melting-point, being gradually decomposed without fusion between 250-280°. A molecular weight determination employing naphthalene gave the high figure 2344, a result very similar to that given in these circumstances by acetyl-santalin itself, and which may possibly be due to the production of a colloidal solution.

Deoxy-iso-santalin, C₂₄H₁₈O₅(OCH₃)₂, corresponding to the deoxysantalin of sanderswood, is a scarlet amorphous powder which has not yet been obtained in a definitely crystalline condition. When heated, it did not show a distinct melting-point but decomposed at 160-165° with evolution of gas. A solution of this substance in absolute alcohol gives no immediate precipitate with potassium acetate, as happens in the case of iso-santalin, and only when excess of the reagent is employed is a gelatinous deposit formed.

A comparison of the colour reactions and dyeing properties of deoxy-iso-santalin (a) and deoxy-santalin (d) is given in the following table:

Alcoholic solution
(a) Orange
(b) Orange-brown

Alcoholic hydrobromic acid
(a) Bright crimson
(b) Scarlet

Dilute sodium hydroxide
(a) Crimson-scarlet
(b) Scarlet

Alcoholic ferric chloride
(a) Violet
(b) Maroon

The dyeing experiments were carried out by the same methods as those described above.

Deoxy-iso-santalin
(a) Pale red-violet
(b) Red puce
(c) Dull red-violet
(d) Pale dull red-violet

Deoxy-santalin
(a) Red
(b) Dull bluish-red
(c) Dull crimson
(d) Red

Acetyl-deoxy-iso-santalin, C₂₄H₂₀O₇(C₂H₃O)₄, when heated, fused and decomposed at 170 175. It consists of an almost colourless powder differing considerably in appearance from acetyl-iso-santalin. A molecular weight determination, employing naphthalene as solvent, gave the figure 1324, which is approximately half that found in the same circumstances for acetyl-iso-santalin.

By exhaustion with alcohol the sample of camwood employed by these authors gave 16 per cent, of extract.

Camwood does not appear to contain either ptero-carpin or homoptero-carpin.