(p. 172) An examination of the outer and inner wood and of the bark of the grey birch, at different seasons of the year, gave the following yields of furfural p.ct. on the dry substance:
| Wood | Bark | ||
| Inner | Outer | ||
| May | 21.3 | 19.6 | 16.7 |
| July | 16.6 | 18.8 | 11.4 |
| October | 16.2 | 16.3 | 12.3 |
The paper contains the results of treating the woods and various vegetable products with hydrolysing agents in order of intensity: (a) Malt-extract at 60°C., (b) boiling dilute HCl (1.0 p.ct. HCl), and (c) boiling dilute HCl (2.5 p.ct.). The residues were found to yield considerable proportions of furfural. The following numbers are typical:
| Birch | Stones of | ||||
| Bark | Wood | Date | Apricot | Peach | |
| Action of malt extract calculated as starch dissolved | 4.24 | 3.5 | 5.2 | 1.5 | — |
| Mannan | |||||
| Residue boiled, 1 p.ct. HCl gave pentosanes dissolved. | — | — | 11.7 | 14.1 | 6.7 |
| Residue yielded furfural | 19.3 | 17.8 | 3.4 | 9.6 | 9.7 |
The proportion of pentosanes (furfuroids) removed, i.e. hydrolysed by boiling with hydrochloric acid of 2.5 p.ct. HCl, is shown by the following estimations of furfural:
| Birch | Sugar maple | Apricot stones | |||
| Bark | Wood | Outer wood | Inner wood | ||
| In original substance | 16.7 | 19.6 | 18.2 | 20.7 | 18.4 |
| In residue from action of 2.5 p.ct. HCl | 6.53 | 8.6 | 4.9 | 6.4 | 7.0 |
Wood Gum.—The paper contains some observations on the various methods of isolating this product. Attention is directed to the necessary impurity of the product, and to the fact that the numbers for furfural and for the xylose yielded by hydrolysis are considerably less than for a pure pentosane.
Estimation of Cellulose.—The author investigated the process of Lange and the 'celluloses' obtained from various raw materials. The products from the woods of birch and maple contained furfural-yielding constituents, represented by yields of 6-8 p.ct. furfural. Preference is given to the process by comparison with others, at the same time that it is recommended in all cases to examine the product for furfural quantitatively, converting the numbers into pentosane equivalents, and subtracting from the total 'cellulose' to give the true cellulose.