378 THE MANUFACTURE OF COD-LITER OIL. 



a bad smell than the common perfectly clear sort, for which reason it has 

 not tin frequently been preferred for medicinal purposes. 



Undoubtedly some of the clear oil is prepared by exposing the liver to 

 a gentle warmth oTer an open fire-place, in iron kettles, whereby a great 

 portion of the oil flows out ; but this method is only adopted in a small 

 way by peasants after their return home, and could not be done on a large 

 scale. 



From the aboTe it will be seen that there are only two principal sorts of 

 cod-liver oil, the so-called clear and light brown, and the dark brown or 

 tanner's oil The first is prepared without, and the other exclusively by, the 

 application of heat ; and it is from this cause that they differ both essentially 

 and apparently. The oil which is prepared by 'steam, or after decomposi- 

 tion without warmth, contains more or less stearin, which it deposits under 

 a temperature of 5deg. C. That whieh is manufactured under such a 

 temperature that the oil will boil contains no stearin, as this is destroyed 

 by the heat. 



The different shades of colour observed in the light coloured oil (and 

 there is an infinite variety) are caused, in some degree, by the colouring 

 properties of the blood, which, as was mentioned above, is absorbed by 

 the oil during the process of decomposition, but principally by the casks, 

 which, under the chemical action of the oil, impart a brownish colour to it. 



This is chiefly the case when the casks are new, and the colour is found 

 to increase in intensity the longer the oil is kept in them, especially when 

 they are placed in a cellar, or in any damp place. In order, therefore, to 

 preserve the original colour, especially when the oil is intended for medi- 

 cinal purposes, it is best to draw it off into large glass bottles. 



The first-named sort of cod-liver oil employed for medicinal purposes, 

 has, hitherto been manufactured without any radical improvement having 

 been adopted in its preparation. 



It is a patent fact that the kinds of cod liver oil described above possess 

 a nauseous smell and taste, so that the patient can with difficulty be 

 brought to take them ; a feeling which would be considerably augmented 

 if the cause of its disgusting odour (which is produced by putrid portions 

 of fish) were known. 



As long as the oil was confined to it original purposes, there was no 

 inducement to advise a better method for its manufacture. 



Different means have indeed been had recourse to, e. g. — lime and caustic 

 kali, to make it better adapted for use in lamps ; but it is easy to see that 

 such treatment would not answer the purpose ; for the alkalies, as is the 

 case in other fatty oils, produce decomposition and form soap, from which 

 glycerine is extracted. Fatty acids cannot be separated from these alkalies 

 without having recourse to a stronger acid. By such treatment, therefore, 

 instead of obtaining a more purified sort, the oil will be in a much more 

 decomposed state. Some of these fatty acids are notorious for their 

 unpleasant smell and rancid flavour. It is, therefore, quite clear that oil 

 prepared in this maimer must be totally unfit for medical use. 



