243 ij.: 



Some Remarks on the Reciprocal Action of Indigo and 

 the Flawed Oils. By Charles H. Weston, Esq. 



[Communicated by the Author.] 



Of the many substances which the experiments of chemists 

 have led us to consider, as primary or simple, there is none 

 of more pervading importance than oxygen ; none capable of 

 accomplishing a greater variety of changes by its combination 

 with other bodies. 



Some of the many and dissimilar effects of oxygen are 

 happily exemplified by the metallic oxides, and all their shades 

 of colour — by oxides of the same metal varying according to 

 the proportion of oxygen absorbed — and by the conversion of 

 many substances into the family of the acids. Among organic 

 bodies, however, indigo stands pre-eminently conspicuous, for 

 beautifully illustrating the diversified consequences of the same 

 agent. These, indeed, in a general way, are known to all per- 

 sons in the least conversant with the nature and properties of 

 this valuable dye. Yet, a more minute knowledge not only 

 discovers that there is no period, in which indigo from first to 

 last (short of decomposition) is not influenced by oxygen, but 

 that the changes resulting from a combination with this gas, 

 vary according to the quantity thus chemically absorbed. ? 



In a paper connected with the subject of indigo, in the 

 Quarterly Journal of Science of June last, I remarked that a 

 certain proportion of oxygen renders the dyeing substance, 

 before it is separated from the leaves of the plant, soluble in 

 water ; that a greater proportion renders it insoluble *, and 

 that a still further accession again renders it soluble. Change 

 of colour, corresponding with these increments of oxygen, in- 

 variably follows, which, commencing with a yellowish green, 



* Hence it follows, that, in proportion as the indigo of commerce imparts to 

 boiling water more or less of the greenish yellow, in the same proportion has the 

 manufacture of it been imperfect. The immediate cause, however, of the presence 

 of this deoxygenized indigo can only be known to the manufacturer, because it 

 may have resulted either from mismanagement in the beating vat — or, if this part of 

 the process had been properly conducted, from the imperfect desiccation of tha 

 leaves, or from want of sufficient sunshine during the growth of the plant. 



