ADVANCED CHEMICAL PHYSIOLOGY 



325 



resulting solution to the boil, and then carefully add powdered zinc 

 carbonate until the reaction is neutral. Filter. Evaporate the nitrate 

 to small bulk, add an equal bulk of spirit and allow to stand, when 

 zinc sarcolactate will crystallise out (Fig. 205). The zinc salt is filtered 

 off, washed several times with spirit, dissolved in water, 1 and the zinc 

 separated by passing a stream of sulphuretted hydrogen through the 

 solution. The zinc-free filtrate is then freed of water by evaporation, 

 when the lactic acid is obtained as a syrup (see also pp. 294, 322). 



FIG. 204. 

 Hypoxanthine silver nitrate. X 300. 



FIG. 205. 

 Zinc sarcolactate. X 300. 



Preparation of Nucleo-Protein. Boil 100-200 gms. finely minced 

 pancreas with about a litre of water for ten to fifteen minutes and then 

 filter. To the filtrate, whilst still warm, add acetic acid drop by drop 

 until a finely- divided precipitate begins to settle out. Filter this 

 precipitate off, wash with water, then very thoroughly with alcohol and 

 finally with ether. It is best to allow the precipitate to stand for some 

 hours in ether, then dry. The dry substance is nucleo -protein. 



Detection of Pentose in the Nucleo-Protein. To a small quantity 



1 The watery solution should be evaporated until the crystals of zinc 

 sarcolactate begin to appear, this being ascertained by examining a drop 

 under the microscope. 



