PHYCOPH.IN PROTEIDS 357 



Phycophaein. The brown coloring matter of the brown 

 algae. It is soluble in fresh water and more readily in hot water, 

 leaving chlorophyll and carotin behind in the plastids. It is 

 insoluble in strong alcohol, ether, etc. 



Piperine, C 17 H 19 NO 3 . Piperine is an alkaloid occurring 

 in the fruit of the Piperaceae, and notably in black pepper, and 

 it has not been found outside this family. Very thin sections 

 may be rubbed out somewhat under a coverglass to press out 

 the ethereal oil, which will then evaporate and leave the piper- 

 ine to crystallize in the form of minute short needles. A sec- 

 tion becomes of a deep red color when treated with concen- 

 trated sulphuric acid, while with nitric acid an orange color 

 is produced. When sections are moistened with sodium molyb- 

 date, and then treated with concentrated sulphuric acid, they 

 take on a blue color. Piperine is easily soluble in acetic acid. 



Proteids (Albuminoid Substances). Proteids are stained 

 from yellow to brown by a dark solution of potassium iodide- 

 iodine. The dilute solution of iodine recommended for starch 

 should not be used, for proteids are stained less readily than 

 starch. Millon's reagent (see under this head in the last chap- 

 ter) colors proteids a brick-red color. If the solution is old 

 and has lost its efficiency, a few drops of a solution of potas- 

 sium nitrate will probably restore it. Concentrated nitric acid 

 colors proteids yellow, and the addition of ammonia produces 

 a still deeper yellow. When sections lie for an hour or tw r o 

 in a solution of r gm. of sodium phospho-molybdate in 90 gm. 

 of distilled water and 5 gm. of nitric acid, which has been filtered 

 after standing for several days, the proteid substances appear 

 in the form of yellowish granules. A concentrated solution 

 of nickel sulphate colors proteid granules yellow or blue. \Vhen 

 rather thin sections are placed in a concentrated solution of copper 

 sulphate for about half an hour, and then are placed in water 

 for about an hour, and then are transferred to a concentrated 

 solution of potassium hydrate, proteids are colored red or violet, 

 which becomes deeper when the solution in which the sections 

 are lying is heated somewhat. The pepsin-glycerine and pan- 



