A HARVEST FROM THE OCEAN. 381 



combustion are lost and the escaped gases overcloud whole town- 

 ships, and impart to miles of sea-shore the peculiar odor charac- 

 teristic of burning kelp. To save these gaseous products by dis- 

 tilling the weeds in closed retorts, at low temperatures, would 

 mean the production, at little extra cost, of valuable amounts of 

 ammonia, parafin, acetic acid, naphtha, etc. In addition, the char- 

 coal left would be much richer in iodine than the ordinary kelp, 

 and its mechanical form much easier of subsequent extraction. 

 Attention has been called time and again to the enormous waste 

 of material and the easy means of improvement in kelp-making, 

 but thus far little inroad has been made into this European species 

 of ancestor-worship. The crofters cling to traditional methods 

 and primitive tools. 



When kelp, such as has been described, is brought into market, 

 it is purchased by those directly engaged in making the salts of 

 iodine and the alkalies. In their hands it becomes the subject of 

 careful treatment to separate the valuable ingredients from the 

 gross impurities with which they are associated. This is commonly 

 done by breaking the kelp into small lumps and lixiviating in 

 suitable vats filled with hot water or supplied with steam vapor. 

 Such treatment, when sufficiently prolonged, dissolves out the 

 alkaline and iodine salts, which need only the subsequent opera- 

 tion of being allowed to settle and siphoning off to separate them 

 from the insoluble matters. The liquor contains chiefly the chlo- 

 rides, the sulphates, the sulphites, and the hyposulphites of sodium 

 and potassium, as well as the iodides and bromides of those metals. 

 By evaporating this solution, the greater portion of the chlorides 

 and sulphates will crystallize out before the iodides, bromides, 

 and lower sulphur compounds begin to deposit. The former may 

 then be fished out of the evaporating pan, leaving a resultant 

 mother-liquor rich in iodides. The hurtful sulphur compounds 

 remaining are decomposed by excess of strong sulphuric acid, and 

 then the proper quantity of manganese dioxide is added. This 

 mixture is transferred to an iron retort and heated, the result of 

 which is to liberate the iodine and part of the bromine present. 

 The vapors of these elements are conducted into proper earthen- 

 ware condensers, where the iodine is deposited as a black powder, 

 and the small quantity of bromine as a dense brown liquid moist- 

 ening the iodine powder. As before indicated, from twelve to 

 twenty pounds of this crude iodine are obtained from the mother- 

 liquor of one ton of kelp. There are several possible ways of puri- 

 fying the crude iodine, in order to secure the iodine of commerce 

 and also the bromine which had been its chief impurity. Even 

 this purified iodine contains minute traces of bromine, owing to 

 the difficulty of their perfect separation. If iodide of potassium 

 is desired instead of free iodine, it is still necessary to produce 



