154 Proceedings of the Royal Irish Academy. 



it contains a large quantity of potash salts and all the sulphuric acid 

 employed in the extraction ; the money value of which is estimated 

 to be nearly one-half of the whole cost for extracting all the products 

 from the kelp. 



Chlorine is the agent, out of the many proposed as substitutes 

 for the manganese oxide and sulphuric acid, which I would recom- 

 mend, but under conditions somewhat different from those I have seen 

 described ; this difference ia the conditions would render the process 

 more exact, and better results in every respect would be obtaiaed. 

 The kelp solution I would render neutral by the addition of sulphuric 

 acid before adding an aqueous solution of chlorine ; and as I have found 

 by investigation that the kelp solution contains clay, and as this sub- 

 stance tends to render the solution viscid and unfavourable for crys- 

 tallization, I would, before evaporating to obtain the last crop of 

 potassic chloride, nearly neutralize the liquid so as to get rid of it. 

 Although a little more acid would be consumed than i£ it were all 

 added in the ulterior stage, the disadvantage would be more than 

 compensated by the larger crop of crystals of potassic chloride which 

 would be obtained, and the greater concentration of the liquid. After 

 the extraction of the last crop of potassic chloride, I would neutralize 

 the liquid exactly, and then place it in a graduated vessel ; I would 

 then add to a small measured portion of it some bisulphide of carbon, 

 and finally some chloriae water from a graduated vessel, until the 

 violet colour just disappeared. This is a process frequently employed 

 for the estimation of iodine, and occupies only a minute or two. Having 

 ascertained the exact quantity of chlorine water which decolourizes the 

 iodine — that is, converts it into pentachloride of iodine — it would only 

 remain to add to the larger measured quantity of the liquid contain- 

 ing the iodine one-sixth of the relative quantity of the chloriae water 

 which was required on the smaller scale. The small portion of iodine 

 which would remain dissolved in the liquid, owing to its slight solu- 

 bility in water, I would remove either by bisulphide of carbon or 

 benzol. After the removal of the iodine, I would treat the liquid 

 with chlorine water, with similar precautions for the removal of the 

 bromine ; but as the compound of chlorine and bromine is a monochlo- 

 ride, one-haK, and not one-sixth, as in the case of the iodine, of the 

 relative quantity of chlorine water would have to be added to the 

 larger measured portion of the liquid. 



If, in any case, it should be found desirable not to precipitate the 

 entire portion of the iodine and bromine with chloriae water, on 

 account of rendering the liquid too dilute, a portion might first be 

 precipitated by chloriae gas, and the remainder by means of chlorine 

 water in the way I have described. 



This method would not only be speedy but exact, for it would be 

 the conversion of a quantitative analytical operation into a manufac- 

 turing process. After the removal of the bromine, the alkaline salts 

 which remained in solution could be easily recovered. 



It wculd be necessary to sublime the precipitated iodiae. 



