04 Prof. A. E. Wright. On the Measurement of [Aug. 5, 



essential to the proper carrying out of the technique described 

 below. 



It will be well, therefore, to commence by describing the method 

 adopted for the preparation of a fatty acid-free oil. 



Method adopted j "or obtaining a Fatty acid-free Oil. 



The method I have employed is a modification of that which was 

 employed by the late Prof. E. Kiilz for obtaining a fatty acid-free oil 

 for experiments in connection with pancreatic digestion. 



The procedure will perhaps be most clearly described by detailing 

 an actual experiment. 



300 c.c. of a cheap variety of table oil (cotton oil ?)* was introduced 

 into a litre flask along with 150 c.c. of half saturated barium hydrate 

 solution. These fluids were digested together at 60° C. on a water 

 bath for three hours, the contents of the flask being well shaken up 

 at intervals. 



After this time the contents had separated into three layers, an 

 upper layer of more or less clear oil, a middle layer, about half an inch 

 deep, of barium soaps, and a lower layer of barium hydrate solution. 



A drop of the supernatant oil was now tested by shaking it up in 

 a test tube with some 0*25 per cent, sodium carbonate solution. Indi- 

 cations of emulsification were quite absent. 



The contents of the flask were now poured upon a wet filter. After 

 the lapse of a few minutes, when the barium hydrate solution had 

 filtered through, a clean dry beaker was placed under the funnel, and 

 the whole filter stand was placed in a warm chamber. By next morn- 

 ing some 200 c.c. of clear oil were found in the beaker, the barium 

 soaps having been left behind on the filter. 



On shaking up the filtered oil with the sodium carbonate solution, it 

 was found that this last showed a trace of turbidity. This turbidity 

 was increased by breathing into the test tube and shaking up again. 



In view of this, the whole volume of oil was now shaken up with 

 distilled water, and a stream of carbonic acid gas was led through. 

 The water and barium carbonate precipitate were then separated from 

 the oil by filtration. When the oil thus purified was shaken up with 

 the sodium carbonate solution, this last remained absolutely clear, the 

 globules of oil remaining distinct and coming up promptly to the 

 surface. 



The fatty acid-free oil thus obtained is introduced into a stoppered 



* The experiment described above can be perhaps even more easily carried out 

 with any of the stable animal oils which are sold for lubricating fine machinery. 

 Unstable oils, such as olive oil, are unsuitable, inasmuch as these last are broken 

 up and converted into soaps when digested, as described above, with the barium 

 hydrate solution. 



