Dr Davidson oti (he Bitter Taste of Iceland Moss, 261 



er solution of the soluble matters than a shorter, for if the 

 bitter principle be completely extracted, it is more than pro- 

 bable that the sugar and gum, as being readily soluble in 

 watery liquids, will also be taken up. And in point of fact, 

 on evaporating the alkaline liquid, after a fortnight's macera- 

 tion, it seemed to contain very little solid matter. 



In one experiment, however, I found the solution made 

 with subcarbonate of potass, become gelatinous, which ap- 

 peared to be ovping to a partial degree of fermentation, for its 

 bitterness was completely destroyed. 



Caustic potass seems to have more effect in extracting the 

 bitter principle than the subcarbonate of potass, a less quan- 

 tity of the alkali being required. T have therefore generally 

 adopted the following process. 



Take 4 lb. of subcarbonate of potass (^potashes) 4 lb. fresh 

 quick-lime. Reduce the lime to powder, by sprinkling up- 

 on it, about a third of its weight of water, and put it and the 

 potash into a jar along with 4 or 5 gallons of water. Cork 

 the jar closely, and agitate it occasionally, for twenty-four 

 hours ; then decant the clear liquid, and pour it upon 112 lb. 

 of Iceland moss placed in deny convenient vessel. Add more 

 water to the jar and agitate, so that the whole of the alkali 

 may be exhausted. Add this also to the Iceland moss, and 

 even an additional quantity of water, so that it may be com- 

 pletely covered. The maceration of the lichen must be con- 

 tinued for about a fortnight, but the time may be longer or 

 .shorter according to circumstances, and its state may be as- 

 certained by taking out of the vessel, a small piece, washing 

 and then chewing it for a minute or so. Straining the lichen 

 by pressure is injurious, as tending to press out a part of the 

 .starchy principle, the water should therefore be simply allow- 

 ed to drain off, before it be dried. As small a quantity of 

 water as possible should be employed for dissolving the po- 

 tass, for a strong solution has more power in extracting the 

 bitter principle than a weak ; it will therefore be found ad- 

 vantageous to divide the lichen into small pieces, as in that 

 form it will have less bulk. The proportion of subcarbonate 

 of potass recommended in this process is 1 to 28 of the Ice- 



