272 PHYSIOLOGICAL CHEMISTRY . 



Analysis of gall stones. Extract gall stone powder with a 

 small volume of ether. Filter through a dry filter, allow ether 

 to evaporate and observe the residue of cholesteriii (1). The ma- 

 terial which did not dissolve in ether consists mainly of inorganic 

 substances and bile pigments. Dissolve out the inorganic ma- 

 terial by adding a small amount of 10% HC1. (See 2 a 

 below.) The filtrate contains inorganic material (2) and the resi- 

 due consists mainly of bile pigments (3). 



1. (a) Examine under a microscope the crystals left on evap- 

 orating the ether extract. If the crystals are not well formed, dis- 

 solve a portion of them in a very small quantity of alcohol and 

 allow to evaporate slowly. Draw crystals. They should be large, 

 colorless plates. 



(b) To a few cholesterin crystals add concentrated H 2 S0 4 and 

 note the red color. 



2. Inorganic Material. Analyze the hydrochloric acid extract 

 obtained above as follows: 



(a) Carbonates. If carbonates were present, an evolution of 

 CO 2 will have been observed on the addition of 10% HC1 above. 



(b) Phosphates. Evaporate a portion of the HC1 extract to 

 dryness on the water bath, take up with a few drops of concen- 

 trated HN0 3 , dilute with a few cubic centimeters of water and 

 add ammonium molybdate in excess. Observe the yellow crystals 

 of ammonium phospho-molybdate. 



(c) Calcium. Evaporate the remainder of the HC1 extract to 

 dryness, take up with a few cubic centimeters of 10% acetic acid 

 and add ammonium oxalate. Calcium oxalate precipitates. 



3. Bile Pigments. The residue insoluble in 10% HC1 is 

 extracted several times with chloroform. A yellow color indicates 

 bilirubin. If time permits, filter the chloroform extract, evapo- 

 rate to dryness and test for bile pigments. The residue insoluble 

 in chloroform may be extracted with a few cubic centimeters of 

 hot alcohol, filtered, evaporated and the resulting residue tested 

 for biliverdin. 



