Dr. Ure on Indigo, 165 



graduated stem, previously filled with hydrogen, by plunging 

 the vessel into the vat, -we may transfer a portion of deoxidized 

 indigo conveniently to the mercurial pneumatic trough, and 

 measure the quantity of oxygen which a given bulk of it ab- 

 sorbs in becoming blue. This quantity will be proportional 

 to the strength and purity of the vat-liquor. I have lately 

 instituted a series of experiments, the results of which will, 

 I hope, prove interesting in reference to the problem for deter- 

 mining the quahty or purity, and strength, of different com- 

 mercial indigoes ; but they are not yet mature enough to meet 

 the public eye. The rigid mode of examining this drug is to 

 eliminate the indigo-blue from the other substances, by the 

 readiest artifices of analysis, and to weigh it apart. It may 

 be objected to the analysis of indigo, that it is too complex and 

 operose a process to be practicable with the despatch and to 

 the extent which the public quarterly sales of indigo require. 

 But I conceive this to be a mistake. When only one object is 

 pursued, various arrangements may be contrived for readily 

 attaining it. Under this conviction, I ventured to state, ten 

 years ago, in the introduction to the first edition of my Die 

 tionary of Chemistry, that ^' the result of numerous researches 

 made with that view, has shewn me the possibility of ren- 

 dering analysis in general a much easier, quicker, and more 

 certain operation, than it seems hitherto to have been in 

 ordinary hands." My experience since has fully justified that 

 statement. 



Accordingly, about three years ago, I suggested to the 

 Honourable Court of Directors of the East India Company, 

 the propriety of establishing an Assay Office for Indigo in 

 Calcutta, to guide them in their purchases of that article, and 

 to enlighten the manufacturers in Bengal about the value of 

 their various products and processes ; and I again submitted to 

 their consideration, last autumn, a memorial to the same effect, 

 in which I detailed the advantages likely to accrue from such 

 establishment to indigo-planters, dealers or brokers, and con- 

 sumers. But the Court did not think it expedient at present 

 to make any alteration in their indigo department. How 

 much an office of this kind is wanted in London, in connexion 

 with the quarterly sales of indigo, the following series of ana- 



