CHAP. II.] 



AREOMETERS OR HYDROMETERS. 



39 



The extreme point of Baume's salimeters is 60 : the hydrometer 

 floats with this point at the surface in monohydrated sulphuric acid ; 

 36 corresponds to nitric acid and 26 to hydrochloric acid. 



The alcoholometer, called also alcohol hydrometer, spirit hydro- 

 meter, and ether hydrometer, is intended to compare liquids of less 

 density than that of water. It is constructed so that, immersed in 

 pure water, the point to which it sinks is near the bottom of the 

 stem (Fig. 17). The graduation starts from zero at this point: on 

 placing the hydrometer in a solution containing 10 per Rent, of sea 

 salt, the difference between the two levels is divided into ten equal 

 parts (degrees), and this scale is continued upwards from zero to 



FIG. 16. Hydrometer for 

 liquids heavier than 

 water. 



FIG. 17. Hydrometer for 

 liquids lighter than 

 water. 



FIG. 18. Gay-Lussac's centesi- 

 mal alcoholometer. 



about 50 : this scale is sufficient for the requirements of industry 

 and commerce. 



The expressions : alcohol at 36, alcohol at 40 indicate that 

 Baume's alcoholometer, immersed in an alcoholic or spirituous liquid, 

 sinks to the divisions 36 or 40 of the hydrometer thus graduated. 



Hydrometers are constructed to determine the richness of wine in 

 alcohol : these are called vinometers ; others to discover if milk does 

 or does not contain water : these are termed lactometers. 



Gay-Lussac's centesimal alcoholometer (Fig. 18) has a great 

 advantage over that constructed by Baume' : its graduation not only 

 indicates the comparative strength of pure alcohol and water in 



