66 LABORATORY EXERCISES 



b. Count the number of cogs in the large wheel of an egg 

 beater. In the small wheel to which the beating apparatus is 

 attached. How many times does the small wheel revolve while 

 the large wheel is turned one revolution? 



c. What kind of a machine is there in the "self-sealing" 

 fruit jar? In the ordinary form? In modern ice skates? In 

 a door catch ? In a window having window weights? In a win- 

 dow fastener? In a key? 



d. Examine carefully a sewing machine, a bicycle, a type- 

 writing machine, a clothes wringer, and a washing machine, and 

 write down all the simple machines you find in each. 



e. What tool is a screw driver when you use it to take a tack 

 out of the floor? To force a screw eye into a board? 



/. Examine a " crosscut" saw, and describe it. Do the 

 same for a "rip" saw. What kind of a simple machine is a 

 saw? 



EXERCISE 64 

 ACIDS 



Apparatus and Materials. Glass or porcelain dishes, test tubes, 

 dilute sulphuric, nitric, hydrochloric, and acetic acids; crystals of 

 tartaric and citric acids; lemons, grapefruit, oranges, tomatoes, sour 

 milk, vinegar, dill pickles, rhubarb; blue litmus paper, ammonia water, 

 tea leaves, apple, dry oak leaves, zinc, copper (wire or cent), iron 

 (filings or tacks). 



a. Taste of Acids. What is the characteristic taste of 

 lemons, grapefruit, oranges, and tomatoes? Of sour milk, 

 vinegar, dill pickles, and rhubarb? 



To 5 cu. cm. of water add a few drops of ordinary, dilute 

 sulphuric acid, and taste the solution; then spit it out. Save 

 the remainder for b. Do the same with a few drops of dilute 

 hydrochloric acid; with dilute nitric acid; with acetic acid. 

 Give the results. 



