70 ANIMAL QTJINOIDINE. 



mined, either directly or after previous drying in a 

 water-oven, with very dilute sulphuric acid, heating the 

 mixture on the water-bath. Repeat this extraction, 

 mix the extracts, filter after cooling, neutralise with 

 caustic soda and repeatedly shake up with ether equal 

 in bulk to that of the extract. Distil off the ether, take 

 up the residue in dilute sulphuric acid, filter, and 

 observe if fluid be clear. 



2. If not clear repeat neutralisation with soda and 

 extraction with ether, and resolution in dilute sulphuric 

 acid. 



3. Treat the solution for fluorescence by exposing it 

 to a cone of sunlight, or of the spark of the Ruhmkorff 

 coil, condensed by a quartz -lens. Observe that the 

 colour produced is bluish-green when the solution is 

 concentrated, but blue when dilute. 



4. Compare this fluorescence with that of a very 

 weak solution of sulphate of quinine in water, and 

 observe its close resemblance to it. 



Benzoic acid, 7 H 6 3 . 1. Obtain benzoic acid by the 

 process described under Acetic acid, 2. 



2. Obtain benzoic acid by boiling hippuric acid with 

 excess of concentrated hydrochloric acid. It will 

 crystallise on cooling. Filter and wash with cold 

 water. Dry in the air without using heat. 



3. Purify the acid by sublimation from a porcelain 

 capsule covered with a diaphragm of filtering paper and 

 a conical hood of paper. 



4. Heat a small quantity of the acid in a glass tube, 

 and observe that it fuses, then is volatilised and again 



