PROBLEM 180 213 



c. Test for Copper 



Materials. — Canned peas or beans, beaker, hydrochloric acid, 

 iron nail. 



Method. — Place half a spoonful of mashed canned peas or 

 beans in a beaker containing one spoonful of water and 10 drops 

 of hydrochloric acid. Set the beaker in a dish of boiling water. 

 Drop a new iron nail into the mixture. Boil for ten minutes. 

 Stir constantly. 



Observations. — What color does the nail turn ? (See note, page 

 212.) 



Conclusion. — Is copper present in the material tested ? 



d. Are Eggs Fresh? 



Materials. — Egg, salt solution. 



Method. — Make a weak (10 per cent) salt solution. Place 

 eggs to be tested in the solution. 



Observations. — Do the eggs you test float? If so, they are 

 fresh. 



Conclusion. — Are the eggs tested fresh ? 



e. To Test Milk for Formaldehyde 



NOTE. — Formaldehyde is an unlawful adulterant. 



Materials. — Milk, beaker, hydrochloric acid, ferric chloride. 



Method. — Put in a beaker a teaspoonful of milk from the dairy 

 that supplies your home or lunch room. Add twice the amount 

 of hydrochloric acid to which a drop of ferric chloride has been 

 added. Mix by rotating the beaker gently. Place the beaker in 

 a pan of boiling water and leave for 5 minutes. 



Observations. — If there is a purple or lavender color, formalde- 

 hyde was present in the milk. 



Conclusion. — Is formaldehyde present in the milk tested ? 



Problem 180: To determine the effect of alcohol upon raw 

 white of egg. 



Materials. — White of egg, alcohol, test tubes. 



NOTE. — In chemical and physical composition the white of egg is nearly 

 like protoplasm. 



