CELL-CONTENTS AND CELL-WALLS. 43 



(6) Treat some Pea flour with 10 per cent, salt solution for several 

 hours, and filter ; test the residue for starch. To portions of the 

 clear filtrate apply the chief protein tests ; then drop some of it 

 into a beaker of water note the precipitate of globulins. 



46. Proteins in Potato Tuber. Scrape the surface of a potato 

 into a beaker ; to the scrapings add some salt solution, stir well, 

 and strain through calico into another beaker. On standing, a 

 deposit of starch is formed ; examine this with the microscope, and 

 test a portion of it with iodine. Pour off the liquid, and apply to 

 it the chief protein tests. 



47. Proteins in Wheat Plour. Make extracts of ordinary 

 wheaten flour with (1) water, (2) salt solution, (3) alcohol. In each 

 case filter, and test the filtrate for proteins. 



Separate the gluten (a mixture of proteins) from the starch, as 

 follows. Enclose a tablespoonful of flour in a piece of fine muslin, 

 and knead it in a basin of water. Note the deposit of starch 

 grains ; examine these with the microscope and compare with those 

 of Potato and Pea. Remove the starch entirely by kneading under 

 a running tap until the water at first whitened by the starch 

 passes off clear ; open the muslin and note the yellowish sticky 

 mass of gluten left behind. 



Extract the gliadin from the gluten by boiling with alcohol, 

 filter, evaporate the alcohol from the filtrate, and apply the protein 

 tests to the residue (gliadin). The insoluble remainder left on the 

 filter contains glutelin ; note that this is insoluble in water and in 

 salt solutions, soluble in dilute acetic acid and in dilute caustic 

 soda. 



Prove the presence of carbon, nitrogen, and sulphur in (1) Pea 

 flour, (2) the "gluten" just isolated from Wheaten flour in the 

 same way as with egg-albumin ( 41, s, t). 



48. Proteins in Brazil Nut. Remove the shells from some 

 seeds, grind up the seeds, and extract with ether to remove the oil ; 

 this may be done best with a Soxhlet fat extraction apparatus 

 ( 97). Allow the ether to eA^aporate, and note the residue of oil. 



Extract about 10 grams of the oil-free nut meal with 50 c.c. of 

 10 per cent, salt solution. Pour some of the extract into about 20 

 times its volume of water in a beaker ; a cloudiness is produced 

 which on standing separates into flakes and falls to the bottom. 

 Then pour off the greater part of the water, and filter the remain- 

 der ; to the precipitate apply the chief protein tests. 



The crystalline globulin (excelsin) of Brazil nut can be obtained 

 in fine hexagonal plates by dialysing the saline extract ; by this 

 method the globulin separates out more slowly than by simply 

 pouring the extract into water. 



