Food and Drink 97 



Experiment 35. Moisten some flour with water until it forms a 

 tough, tenacious dough ; tie it in a piece of cotton cloth, and knead 

 it in a vessel containing water until all the starch is separated. There 

 remains on the cloth a grayish white, sticky, elastic "gluten," made 

 up of albumin, some of the ash, and fats. Draw out some of the 

 gluten into threads and observe its tenacious character. 



Experiment 36. Use fresh cow's milk. Examine the naked-eye 

 character of the milk. Test its reaction with litmus paper. It is 

 usually neutral or slightly alkaline. 



Experiment 37. Examine with the microscope a drop of milk, not- 

 ing numerous small, highly refractive oil globules floating in a fluid. 



Experiment 38. Take one or two teaspoonf uls of fresh milk in a test 

 tube ; heat it until it is lukewarm, and add a small quantity of liquid 

 rennet. Note that the whole mass curdles in a few minutes, so that 

 the tube can be inverted without the curd falling out. Soon the curd 

 shrinks and squeezes out a clear, slightly yellowish fluid, the whey. 



Experiment 39. Place some Fehling's solution (which can be 

 obtained readily at the drug store, or tablets may be bought which 

 answer the same purpose) in a test tube, and boil. If no yellow 

 discoloration takes place, it is in good condition. Add a few drops 

 of grape or milk sugar solution and boil, when the mixture suddenly 

 turns to an opaque yellow or red color. 



Experiment 40. Mix an even teaspoonful of wheat flour, Indian 

 meal, oatmeal, or rye meal with an equal volume of ether. 1 Stir 

 carefully and filter mixture after it has stood for fifteen minutes to 

 get rid of the ether odor. Evaporate some of the filtrate on a watch 

 glass. A greasy residue is left, which may be shown by rubbing it 

 on a piece of tissue or rice paper. 



1 Benzine may be used instead of ether, as it is much cheaper and more 

 readily obtained. As its vapor, as well as that of ether, is highly inflam- 

 mable, the greatest caution must be exercised not to handle it near a flame 

 or a hot stove. 



