IODINE NUMBER OF LIPIDS 295 



Schmidt-Nielsen Method for Iodine Nunil>er 



SPECIAL REAGENTS 



Cellosolve (glycol monobutyl ether). Redistill and store in the 

 cold. 



1 % Potassium Iodide Solution. Store in the dark. 



0.1% Soluble Starch Solution. Stir up 0.1 g. in 10 ml. cold water 

 and pour, with stirring, into 90 ml. water at 76°. Store at 0°. 

 Vs or ^/e N Bromine Solution. (May be made weaker.) Saturate 

 methyl alcohol with sodium bromide (about 13 g./lOO ml.); 

 filter and add 10% more methyl alcohol. Dissolve the bromine 

 in this soln. Store in the dark. Transfer some into a bottle with 

 a small opening to minimize the evaporation of alcohol while being 

 used. 



0.05 N Sodium Thiosidfate. Stabilize by adding 0.2 g. sodium 

 carbonate per liter. 



Pure Toluol. 



PROCEDURE 



1. Pipette the sample dissolved in toluol into the bottom of a 

 paraffined reaction tube (page 169). 



2. Evaporate the toluol in a desiccator over paraffin shavings at 

 a pressure of 20 mm. mercury. 



3. Introduce a stirring "flea" and pipette 5 /A. Cellosolve into 

 the bottom of the tube. 



4. Place a seal of the potassium iodide soln. (about 45—50 ^1.) 

 across the lumen of the tube about one third of the tube length above 

 the bottom, and follow with a similar seal of the starch soln. about 

 one third from the top. The paraffin coating prevents the seals from 

 running. Place the seals by holding the tube horizontally. Introduce 

 the tip of the pipette to the proper position and have it just touch 

 the wall. Blow out the liquid while rotating the tube. Finally cap 

 the tube. 



5. Use the "flea" to dissolve the lipid in the Cellosolve. Some 

 creeping of the lipid occurs during the evaporation of toluol and 

 all this lipid must be incorporated in the Cellosolve. The paraffin 

 coating is insoluble in Cellosolve. 



6. Introduce 2.5 [A. bromine soln. into the bottom of the tube, 



