xxii Proceedings. [April yth, igo8. 



morphosis in the transformation to marble, are rarely perfect, 

 but generally occur as cleavage plates, due to shearing. Many 

 of the crystals appear to have split up, and look almost like cross 

 sections, being hexagonal. Mr. Pettigrew has also found an 

 insoluble residue when clear crystallised calcite or calc spar 

 from Derbyshire is dissolved in hydrochloric acid. This 

 residue consists of pyrites and of quartz, with moulds or hollows 

 showing where the pyrites have been imbedded. The quartz 

 crystals are cubic, and show in most cases exact counterparts of 

 pyrites crystals, proving them to be pseudomorphs, after pyrites. 

 This shows, of course, that the pyrites crystals were formed first, 

 and that the silica is due to a secondary process of crystallisation 

 by replacement. 



Professor Edmund Knecht, Ph.D., M.Sc.Tech., F.I.C., 

 read the following paper, entitled " Note on the Action of 

 Oxalic Acid on Cellulose. " 



Although oxalic acid has been used in calico printing for a 

 very long time, it has not until comparatively recently been 

 supposed to exert an influence upon cellulose difl'erent to that 

 of any other acid of similar strength. In 1902, however, there 

 appeared in The Dyer and Calico Printer an anonymous article 

 (which I have since ascertained was written by one of my former 

 students, Mr. H. H. Pilkington), in which it is pointed out that 

 if calico is printed with thickened oxalic acid, and is then 

 allowed to dry in a cool place for twelve hours, and subsequently 

 washed, the printed parts show an increased affinity for basic 

 colours, and a decreased afifinity for so-called direct colours. The 

 cloth is not tendered in the printed places. Citric and tartaric 

 acids do not produce this effect. The author merely recorded 

 these interesting facts, but offered no explanation. 



In view of these interesting results it appeared to me 

 desirable to attempt to find some explanation of this remarkable 

 behaviour of oxalic acid, and I consequently first repeated the 

 experiments, and was able to verify the results. 



I found that by boiling the treated fabric first in alcohol, and 



