i 



Beport on Dr Davidson's Fapirs. 265 



these processes were tried and found to succeed ; the bitter 

 taste being almost, if not altogether, removed from Iceland 

 moss ; and after removal of the taste, the bleaching process 

 was applied, and the colour, though not entirely, yet was very 

 much discharged. 



III. On the Removal of the Fetid Odour of Fish Oils. {556). 



This process consists also in the use of chloride of lime. It 

 was tried, as recommended, on two samples of oils mentioned 

 by Dr Davidson, viz. seal oil and ?vhale oil. Though these 

 were affected by the chloride, yet they were by no means de- 

 prived of theu' odom*. Dr D, states that chloride has no eflPect 

 on the proper or natural odour of the oils, but seems to be 

 confined chiefly to the removal of the fetor, which is the result 

 of putrefaction. Whether the odour of the oils tried was 

 caused by putrefaction or not I cannot say, but certainly the 

 odour was little altered by the chloride. Supposing the chlo- 

 ride to remove the odour, there is an objection to its use, but 

 which may perhaps by experience be overcome. I allude to 

 the action of the lime on the oil, and the formation of soap, 

 or carron oil as it is commonly called ; which not only wastes 

 the oil, but renders it difficult to separate it from the impuri- 

 ties. Shaking with water after the mixtm-e has been boiled, 

 as recommended, ^vith oil of vitriol miich diluted, causes, after 

 rest, the subsidence of sulphate of lime, but still the oil con- 

 tinues milky. I found it necessary to filter the oil through 

 bibulous paper, so as to get it of its original transparency. 



Samples of seal oil and whale oil submitted to the process 

 are sent. 



IV. On the Adulteration of Fixed Oils. (554). 



In investigating this subject two objects were kept in view. 

 1st, Whether the test proposed is a good one ; and 2d, sup- 

 posing it to be good, whether means might be adopted to pre- 

 vent it from acting as a test. The test proposed, which ap- 

 plies solely to linseed oil, when used as the means of adulte- 

 ration, is alcohol of specific gravity 815 ; which, according to 

 Dr Davidson, acquires a yellowish-green tinge when shaken 

 with the oil. I have found that this is the case, and that as 



