ANALYSIS OF BUTTER-FAT. 71 



numbers, such as not infrequently pour in upon the Public 

 Analyst, every unnecessary step, be it ever so small, must 

 be avoided. Conceding even, for sake of argument, an equal 

 accuracy to the determination of the soluble acids, as to that 

 of the insoluble acids, yet the latter is to be preferred, 

 because the quantities obtained are larger, because something 

 tangible is obtained, and the characters of the fatty acids, 

 such as smell, colour, and melting point may be noted if neces- 

 sary, whilst the determination of the soluble acids being an 

 indirect one no tangible substance is extracted from the butter, 

 and because, lastly, the results are obtained easier and quicker. 



A stronger reason against the introduction of the determi- 

 nation of the soluble fatty acids, in order to detect adultera- 

 tion, is the following : The soluble acids can only be washed 

 out of the insoluble acids with great difficulty. Boiling water 

 is absolutely indispensable if this washing is to be done 

 thoroughly, and loss of the soluble acids by evaporation is 

 therefore hardly avoidable. The saponification is to be per- 

 formed in a closed flask, because butyric ether largely escapes 

 if the vessel be open ; the washing has to be done under the 

 same precautions, and yet the filtering or the pouring off must 

 bring along with it loss and error, however small. 



If, however, the washing is not properly done (and it is most 

 difficult to wash even 10 grammes of butter acids thoroughly 

 and efficiently, as no less than 2J or 3 litres of boiling water 

 are requisite), part of the soluble acids remains with the 

 insoluble members of the group, and slowly volatilises on 

 drying at 100 C. ; thus no error, at least no serious one, 

 is introduced into the determination of the insoluble acids^ 

 but that of the soluble becomes utterly wrong, and unworthy 

 of any importance being attached to it. In the large bulk 

 of wash water necessarily used accurate determination of 

 the minute quantities of soluble volatile acids is in itself a 

 impossibility. 



