Mr. F. C. Calvert on the Adulteration of Oils. 103 



The most difficult pai-t of my researches has been to procure 

 oils the purity of which I could depend on, and to arrive at this 

 object I was obliged in many cases to obtain samples from their 

 sources of production on the Continent ; and even then I took 

 the precaution of ascertaining their degree of purity by applying 

 to them the various tests which I shall describe further on. 



The reason why I employed so many reagents is, that the 

 adulterations which commercial interests may have or dictate, 

 are numerous; and tliat the reactions presented by organic 

 substances, and especially oils, are exceedingly delicate. I would 

 strongly recommend that samples of pure oil be tested compa- 

 ratively with those suspected of being adulterated, and never to 

 apply one only of the proposed tests, but all those giving cha- 

 racteristic reactions with a given oil. 



I have great pleasure in acknowledging the intelligence, in- 

 dustry, and chemical knowledge exhibited in these tedious 

 researches by my assistant, Mr. Charles Lowe. 



As the reactions presented by the various oils depend upon 

 the special strengths and purity of the reagents, not only great 

 care should be taken in their preparation, but also the exact 

 mode and time required for the chemical action to become appa- 

 rent should be attended to ; these I liave taken care to give with 

 each reagent. 



Caustic Soda Solution of spec. grav. 1'340. — The reactions 

 given in the following table are obtained by adding one vol. of 

 the above test-liquor to five vols, of oil, well mixing them, and 

 then heating the mixture to its point of ebullition : — 



Dark colorations. Light colorations. 



(~ ^- -, i " V 



Fish oils, \ egetable oils. Animal oils. Vegetable oils. 



s?r:;lred. ^-p-''{*i:KZ; >^«^ot{'"^^^y^{g; ^y/p^-M^X. 



Cod liver J Linseed., yellow fluid. , , /pinkish- French nut . . { ish- 



\ white. Sesame J white. 



Castor 1 



India nut )■ white. 

 (thick) J 



o&".::::}y^"ow. 



Caustic soda of spec. grav. 1*340 is principally useful to 

 distinguish fisli from other animal and vegetable oils, owing to 

 the distinct red colour which the former assume, and which 

 coloration is so distinct, that 1 per cent, of fish oil can be de- 

 tected in any of the others. This table should also be consulted 

 when tiie question is, not to discover other adulterations, but to 

 distinguish some of the oils : for instance, hempseed acquires a 

 brown yellow colour, and becomes so thick tliut the vessel which 

 contains it may be inverted without losing any of its contents, 



