324 BUTTER. 



A more simple formula , whicli gives nearly as good results, is 



K - (01 P + 0-24 ) 

 " ' 0-244 



Paal and Amberger distil the fatty acids from 2 '5 grammes 

 of butter in steam in a special apparatus, collect 200 c.c. of dis- 

 tillate in from 35 to 40 minutes, wash out the condenser by 

 distilling 50 c.c. of neutral alcohol. The combined distillates 

 are neutralised, and evaporated, made up to 50 c.c, and 2 to 

 4 c.c. of a 20 per cent, cadmium sulphate solution are added. 

 The precipitate is collected on a Gooch Crucible, washed with 

 not more than 50 c.c. of water, dried, and weighed. The weight, 

 calculated as milligrammes, gives the cadmium figure. The 

 figure for butter usually lies between 70 and 90, and for coco- 

 nut oil 441 to 470 ; higher results (100 or above) were obtained 

 from the fat of milk yielded by cows fed on large quantities of 

 coco-nut cake or beetroot lea-ves. 



Estimation of Saponification Equivalent, or alkali neces- 

 sary for complete saponification. 



Kcettstorfer's Method. — Kcettstorfer proposed to utilise the 

 fact that butter required a greater amount of alkali for its com- 

 plete saponification than most other fats. 



The method is performed as follows : — A standard alcoholic 

 solution of sodium hydroxide is prepared by dissolving 25 c.c. of 

 the 50 per cent, solution of caustic soda recommended by Wollny 

 (p. 317) in 1 litre of strong alcohol ; after a day's repose, during 

 which a little salt settles out, the solution is clear and fit for use. 

 This solution, which should be approximately semi-normal, 

 is standardised against semi-normal hydrochloric acid. About 

 2 grammes of the fat are weighed out into a small flask, 25 c.c. 

 of the alcoholic soda solution run in from a pipette, the flask- 

 connected with an inverted condenser, and the contents gently 

 boiled for fifteen minutes. During the boiling the alcoholic soda 

 solution is standardised ; 25 c.c. of the solution are measured 

 from the same pipette, which is allowed to drain for the same 

 length of time as before, and titrated with semi-normal hydro- 

 chloric acid — a little phenolphthalein being added as indicator. 

 The number of cubic centimetres of hydrochloric acid solution 

 should be noted. It is advisable to perform this operation in 

 duplicate. The flask containing the saponified fat is discon- 

 nected from the condenser, a few drops of phenolphthalein 

 solution added, and the liquid titrated with semi-normal hydro- 

 chloric acid till the pink colour just disappears. The number of 

 cubic centimetres used, subtracted from the number required by 

 the 25 c.c. of soda solution alone, wOl give the equivalent of the 



