The chlorine-sodium sulphite colour reaction of woody tissues.

IN a recent paper by Cohen & Harris [1937] it is shown that the lignin of maple wood is, to a limited extent, soluble in hot dilute sulphuric acid and also in hot water. That a fraction of lignin is soluble in water has been suspected for many years and recently it has been definitely suggested by Paloheimo [1929]. The solubility of lignin in dilute acids is discussed by Schorger [1926, p. 92] and Hawley & Wise [1926, p. 70], and only recently it has been shown that the lignin of beech wood is soluble in hot 10 0 sulphuric acid [Bamford & Campbell, 1936]. The study of the action of dilute sulphuric acid and of hot water on the chemical composition of various woods has been in progress in this Laboratory during the past few years. Results so far obtained indicate that treatment of oak sapwood with water at 98° for periods over 100 hr. results in the solution or decomposition of approximately 20% of the apparent lignin, while continuous treatment of oak heartwood with 1% sulphuric acid under the same conditions for 17 days causes the solution or decomposition of some 34%0 of the apparent lignin. The object of the present communication is to record some recent observations concerning the pink coloration which develops after sodium sulphite is added to hardwoods or their extracts after chlorination and treatment with sulphurouis acid. Cohen & Harris [1937] have used this well-known but little studied colour reaction as a confirmatory test for the presence of lignin in the aqueous and acid extracts of maple wood but, as the following results will show, little reliance can be placed upon their conclusions.