The Chemistry of Dendr Growths in Paper. 227 



3. Chemistry of Paper Deterioration. 



Apart from a purely academic interest in the chemistry of these 

 curious growths, the author has followed up this matter from a 

 more important point of view — viz. with reference to the chemical 

 reactions taking place during the deterioration of paper by age. 



The periodic oxidation and reduction actions which take place 

 during the growth of dendrites in paper may be regarded as going 

 on simultaneously as phases of one set of chemical reactions, in 

 which the chief factors are the organic matter of the paper, chemical 

 residues in the latter, and atmospheric oxygen. It is suggested, in 

 fact, that the dendritic growths are visible indicators, by means of 

 secondary reactions, of chemical actions going on in the pores of all 

 paper during ageing, and resulting in the hydrolysis and oxidation 

 of the cellulose. 



This conclusion confirms a previous research* of the writer's, 

 in which he pointed out that certain chemical reactions, which take 

 place in glass only at elevated temperatures, occur in the pores of 

 cellulose at ordinary temperatures, 



4. Micro-Chemical Eeactions. 



The detection of copper sulpliide in these dendritic growths was 

 demonstrated chiefly by the fact that this substance is only soluble 

 with great difficulty in mineral acids, but readily soluble in a 

 solution of potassium cyanide. 



On application of a drop of potassium cyanide solution 

 (equivalent strength) to a dendrite of recent growth, the copper 

 sulphide readily dissolves in the cold forming the soluble double 

 cyanide of copper and potassium, and also potassium sulphide. 

 Further, on adding to this solution a drop of sodium nitro-prusside 

 (one-fifth equivalent strength), the evanescent violet coloration 

 characteristic of the reaction with alkaline sulphides is readily 

 observed, but this test is so delicate for minute quantities of sulphur 

 that some chemists might object to its application in the presence 

 of other chemical residues. It is to be noted however that even 

 in papers containing sulphur in the form of ultramarine, this test 

 gives a negative result on any portion of the paper except that 

 touching a dendritic growth. In the writer's opinion it is quite 

 a satisfactory test because experiments have shown that the 

 production of the violet coloration with potassium sulphide is not 

 affected by any of the chemical residues present. 



However, to make matters more certain in the detection of 



* " On the ' Hughes' Reaction ' of Potassium Iodide on Paper," Chem. News, 

 ciii., pp. 193-6. 



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