FOOD MATERIALS AND HOW TO DETECT THEM 27 



The Soudan III Test 



Directions. Make a grease spot on a piece of filter paper, 

 using any substance which contains fats or oils. Saturate 

 the paper with Soudan III and then wash it with alcohol. 

 What occurs? 



Repeat, using paraffin, beeswax, cocoa butter, vaseline, etc. 

 How may oils be detected ? 



Note. Soudan III is a stain used as a reagent in microscopic 

 work. 



Suggestion. Make a list of oils and fats and the plants 

 or animals which produce them. 



Find out at least one use for each and any interesting 

 facts concerning their manufacture. 



To a test tube half full of water add a few drops of oil. 

 Do they mix? Shake the tube vigorously and note the 

 result. Add a few drops of caustic soda and shake the tube. 

 Result ? Examine a drop of milk under a cover glass, using 

 a low power of the microscope. Draw. 



Select several articles of food such- as bread, cereals, meat, 

 cheese, potatoes, etc., and test each for protein, starch, 

 sugars, and fats. Which contain most of each nutrient? 

 Tabulate your results. 



The Alcanna Test 



Make a solution of alcanna root in 95 per cent alcohol. 

 Filter it and add an equal bulk of water. This solution 

 gives a deep red color to oils and fats. 



Suggestion. Make very thin sections of castor bean 

 or Brazil nut and examine for oil globules. Run a drop of 

 the alcanna solution under the cover glass and watch the oil 

 globules as they take up the color. 



