544 Transactions of the Soci< ty. 



XVI. — On Dendritic Growths of Copper Oxide in Paper. 

 By James Strachan. 



(Read April 15, 1908.) 

 Plate XIII. 



I. Introduction. 



The occurrence of dendritic growths in paper has been observed 

 for a long time, but it is only within recent years that their pre- 

 cise nature has been determined. They were mistaken at first for 

 vegetable or fungoid growths, and were designated by such names 

 as Conferva dendritica (Agardh and Lyngbye) and Dematium 

 olivaceum (Schumacher).* In the year 1872, however, Liversidge f 

 established the fact that the dendritic growths in paper contain 

 copper, and are purely inorganic in their composition. There 

 appears to have been some doubt at this time as to the nature of 

 the copper compound composing the dendrites, whether sulphide 

 or oxide, and Tait \ was among the first to point out that these 

 growths are probably derived from the oxidation of metallic 

 particles imbedded in the paper during manufacture. Tait esti- 

 mated, from an examination of various books containing dendrites, 

 that it required a period of at least twenty years for the develop- 

 ment of these growths. Doubts concerning the true nature of 

 dendrites persisted for a number of years, until in 1901 the whole 

 subject was reviewed and gone into by Scales,§ who came to 

 the following conclusions, from a careful microscopical and micro- 

 chemical examination of dendrites in various kinds of paper : — 



1. That the dendrites in paper are composed of copper oxide 

 with a central metallic nucleus. 



2. That the metallic particles from which the dendrites grow 



* Vide Carrington's remarks on this subject in Science Gossip, i. (1895) p. 268. 



t Journ. Chem. Soc, x. (1872) p. 646. 

 ' J Crystals Bred in Books. Science Gossip, i. (1895) p. 85. 



§ Dendritic Spots in Paper, by F. S. Scales, F.R.M.S. Science Gossip, vii. n.s. 

 (1901) p. 258, et seq. (2 photomicrographs). 



EXPLANATION OF PLATE XIII. 



Fig. 1. — Dendritic growth of copper oxide in paper, containing 70-75 p.c. wood 

 cellulose fibres ; fourteen months' growth, x 20. 

 ,, 2. — Dendritic growth of copper oxide in paper, composed purely of wood 

 cellulose ; about five years' growth, x 12, 



