USES OF CARBON DIOXIDE IN COOKING 233 



4. What happens when a bottle of milk freezes? 



5. Why should milk bottles full of milk never be left on a door 

 step to freeze in the winter? (Suggestion stray dog or cat.) 



6. Why should a small box with a cover be placed outside the 

 house so that the milkman can place the milk in it? 



7. Why is milk sometimes adulterated? 



8. How may we determine whether milk has sufficient fat? 



9. Some cows, as the Durham, do not give milk rich enough in 

 fat to meet the standard requirement of butter fat. 



What cows must the farmer keep in his herd to bring the butter 

 fat of the milk up to standard? 



10. Why is it essential to know the total amount of solid matter 

 in milk? 



11. Why is formaldehyde objectionable in milk? 



12. Why is any preservative objectionable in milk? 



13. Why do cities and towns often require that milk be sterilized? 



14. Project. Find out the requirements of the Board of Health 

 in your town or city regarding milk. 



USES OF CARBON DIOXIDE IN COOKING 



Use of Ammonium Carbonate. Sometimes ammonium car- 

 bonate, as a fine powder, or as a solution, is mixed with flour in order 

 to form a gas for raising dough during the process of baking. The 

 ammonium carbonate changes into ammonium gas, water, and carbon 

 dioxide. Bakers have added ammonium carbonate and yeast to 

 bread in order to make the bread light and the loaf very large. 

 Ammonium carbonate will overcome the sourness of bread, but 

 bread made this way is usually dry and tasteless. 



Use of Baking Soda. Another way of raising bread is through 

 the use of sodium bicarbonate (baking soda). This salt, when 

 heated, gives off carbon dioxide and water, but the product left 

 in the bread is very unwholesome. 



Use of Hydrochloric Acid and Baking Soda. We have learned 

 that an acid and a carbonate produce carbon dioxide. This method 

 of producing carbon dioxide has been used for raising bread. Hydro- 

 chloric acid and baking soda produce carbon dioxide and common 



