LIPID 291 



titration was described by Weil (1936) (page 306), and an electro- 

 metric formol procedure by Borsook and Dubnoff (1939). Sisco, 

 Cunningham, and Kirk (1941) employed their glass electrode (Fig. 

 70, page 184 ) for the electrometric titration, and they also used an 

 indicator method in which the titration is carried out in an open drop 

 but differing little from the procedure of Weil. 



LIPID 



A clever microtitration technique for the measurement of lipid in 

 quantities of the order of 10 fig., suited for the determination on 1 

 mg. of tissue, with a precision of about 1% was developed by 

 Schmidt-Nielsen (1942). The method is based on saponification of 

 the lipid in a sealed capillary tube by alcoholic alkali in the presence 

 of toluol, liberation of free fatty acid by the addition of an excess 

 of mineral acid, solution of the fatty acid in the toluol phase, and 

 titration of an aliquot of the toluol layer after the toluol has been 

 evaporated. 



Schmidt-Nielsen Method for Lipid 



SPECIAL REAGENTS 



Pure Toluol. 



1 N Potassium Hydroxide in Absolute Alcohol (aldehyde free). 



0.5 N Hydrochloric Acid. 



0.01% Thymol Blue in Absolute Alcohol. 



0.02 N Alcoholic Tetramethylammonium Hydroxide. 



PROCEDURE 



1. Pipette the lipid sample in 20 lA. toluol into the bottom of a 

 thin-walled capillary tube having an internal diameter of about 

 1.8 mm. and a length of about 50 mm. Clamp the pipette vertically 

 and raise the capillary tube, placed in a holder, on a mechanical 

 stand so that the tip of the pipette will not touch the sides of the 

 tube as it is raised. Use constriction pipettes for all pipettings. 

 Exercise care to avoid evaporation of toluol in steps 1-6. 



2. In the same way pipette 2.5 p\. alcoholic potassium hydroxide 

 into the toluol soln. and immediately seal the opening of the capil- 

 lary. 



