LABORATORY MANIPULATION 25 



test-tube, when filled with water, holds from 60 to 65 cc. 

 Take a measuring cylinder or graduate (Fig. 6), measure 

 out 5 cc. of water, and transfer to a large test- 

 tube. Note the quantity, and then pour it 

 out. Now draw water directly into the test- 

 tube until you have approximately the same 

 amount, then measure it. Repeat this opera- 

 tion until you can judge with a fair degree of 

 accuracy the part of a test-tube filled by 5 cc. 

 Then repeat the operation, using 10, 15, 20, 

 and 25 cc. portions, until the eye has become 

 reasonably familiar with these approximate 

 and relative amounts ; so that, if at any time Fig. 6. 

 a graduate is not at hand, the amounts can be ^yiSSer 8 

 estimated with the eye accurately enough for practical 

 purposes. 



29. Obtaining Reagents from Bottles. Take the bot- 

 tle from the shelf, remove 

 the stopper, holding it be- 

 tween the first and second 

 fingers of the right or left 

 hand (Fig. 7). Hold the 

 test-tube or vessel that is 

 to receive the reagent in 

 the other hand. Pour out 

 the liquid slowly until the 

 desired amount is obtained. 

 Because of danger of con- 

 Fig. 7. -Pouring liquid from bottle, taminating the reagents, it 

 is always better to pour the liquid slowly and secure the 



