FIG. 8. A 2-bottle hand tester. 



die acid guaranteed to be of the proper strength, and if 

 kept in well-stoppered containers it will not change. For 

 the benefit of those who prefer to test the acid themselves, 

 the following directions are given: 



Use of the acid hy- 

 drometer. This is a 

 hydrometer designed 

 only for liquids hav- 

 ing a specific gravity* 

 about that of concen- 

 trated sulphuric acid. 

 (See fig. 12.) It is 

 standardized at 60 F., 

 and for correct results 

 must be used with acid 

 at that temperature 

 only. The acid at this 

 temperature is poured into the hydrometer cylinder and 

 the hydrometer allowed to float in it. When it has come 

 to rest, the point on the scale intercepting the surface of 

 the acid indicates the specific gravity. If it is much under 

 1.82 it can not be used for 

 testing milk, and should 

 be discarded and a fresh 

 lot of acid obtained. If it 

 is above 1.83 it may be 

 diluted with water until it 

 is of the proper strength. 

 There are two ways of 

 doing this. The acid may 

 be exposed to the air un- 

 til it absorbs sufficient 

 water to lower its specific 

 gravity; this is the safest and best way if the specific 

 gravity of the acid is not much above the standard. 

 The second way is to mix the acid with a small quantity 

 of water. A small quantity of water is placed in a bottle 

 or jar and the acid poured into it. Never pour water into 

 acid, as a serious accident may result. After the mixture 

 has cooled to 60 F. it is again tested with the hydrometer 

 and the process repeated if necessary. 



FIG. 9. A hand tester for 12 bottles. 



