848 JOURNAL OF FORESTRY 



These results show that "black wood" is not constantly characterized 

 by a large amount of iron. It should also be noted that in many 

 cases a consideration of these results and the supposed existence of 

 tannin, which might be of an insoluble form, might be deceptive in a 

 discussion of wood staining. 



(c) While it was impossible to extract the color from shavings of 

 "Jindai-Sugi" ^ and from shavings of Castanea or Pasania woo'i col- 

 ored deep blue with ferric chloride by infusing in water, shavings of 

 "black wood," infused immediately after discoloring, were soon some- 

 what bleached, giving the extract a red or purplish red color. Color- 

 extraction proceeded much more rapidly in alcohol, usually resulting 

 in a deep red infusion. These experiments showed that the coloring 

 matter concerned in this phenomenon is somewhat soluble, while 

 tannin-ferrous compounds were found to be insoluble. They could not 

 have been present in the infusions. 



{d) Whereas the tint of "Jindai-Sugi" and that of Castanea and 

 Pasania stained by ferric chloride were very stable, the dark brown 

 color of "black wood" was unstable, under ordinary conditions chang- 

 mg to brown in a few days and then bleaching out gradually to grayish 

 brown, reaching the final stage after a few months. The fading was 

 not due to the incidental seasoning of the wood as was easily proved 

 by its inability to regain its former color when it was returned to its 

 original moist condition by wetting ; there had been, therefore, a chem- 

 ical change, going on step by step. 



i^e) The darkening of freshly prepared "black wood" could be pre- 

 vented" by soaking in water, so that the chemical substances responsible 

 for the phenomenon, or one of them a.t least, were extracted by the 

 treatment. Several sets of tests with ferric chloride, however, gave 

 no evidence of the existence of tannin in these infusions, except the 

 green color reaction which disappeared upon shaking and which was 

 apparently due to the remnants of catechol abundant in the fresh sap- 

 wood of "Sugi." Owing to the existence of some particular organic 



" "Jindai-Sugi," which is highly prized for ornamental purposes, is, in reality, 

 nothing else than "Sugi" wood at the earliest stage of fossilization, having been 

 accidentally buried for a long tin'e. A large quantity of imitation wood is manu- 

 factured by several artificial methods. There is a well-accepted hypothesis that 

 the deepening of its tint on exposure to air is due to the ferrous oxide present in 

 the wood being oxidized to ferric chloride, which is able to combine with tannin 

 and cause the color change. But the tint when once produced is of long duration. 



