8o 



CHEMISTRY FOR AGRICULTURAL STUDENTS 



of sodium. Hydrochloric acid and sodium chloride have been 

 found by experiment to contain 97.25 and 60.6 per cent, of 

 chlorine respectively. What are the simplest formulae that 

 represent their composition? 



What are the reacting proportions of caustic soda and 

 hydrochloric acid? If chloride of sodium be obtained by 

 neutralising hydroxide of sodium with chloride of hydrogen, 

 hydroxide of hydrogen (water) must be set free, and the salt 

 will weigh less than the base and acid taken by the water 

 formed. Investigate these problems by the following 

 experiment. 



First find the strength of the saturated solution of hydrochloric 

 acid prepared in the preceding experiment. This can be done 

 most easily by determining the density, as the density of a 

 liquid varies with the dissolved constituents. Make two 

 determinations at 15° C. by the U tube method (Fig. 18), and 

 calculate the strength from the following figures : — 



Relative Densities of Solutions of Hydrochloric Acid at 15° C. 



Weigh out 25 grams of the acid into a quarter-liter flask, 

 and make up to 250 c.c. with distilled water measured at 

 15° C. Fill a burette with the dilute acid. Weigh out two 

 portions of caustic soda (say 2 grams each) into two flasks, 

 dissolve in water, add enough litmus solution to render just 

 blue and titrate with the acid, using all the precautions 

 described in Study XVIII. When concordant results have been 

 obtained, calculate the reacting proportions of caustic soda and 

 hydrochloric acid. Do they correspond with the equation 



