292 VIII. ACIDS. 



quantity of pure sulphuric acid (36 parts) necessary to saturate 

 100 parts of subcarbonate of soda, being esteemed as 100 acidi- 

 metric degrees. Then if upon trial 88 grains of any other acid 

 be required to saturate 100 grains; or, for the sake of using 

 smaller quantities, 22 grains should saturate 25 of subcarbonate 

 of soda ; then, as 88 (22) of the acid is equivalent in force to 

 36 (9) of sulphuric acid, so by inverse proportion are 100 acidi- 

 metric degrees to 40 deg. '99, the conventional strength of the acid 

 assayed, which may be quoted as 41 acidimetric degrees strong. 



There are other modes of calculating the strength of acids in 

 this mode of valuation, which is substituted for the equivalents 

 of Dr. Wollaston, with a view of rendering the calculations more 

 adapted to the habits of practical men. 



As the power possessed by 36 parts of oil of vitriol to saturate 

 100 parts of dry subcarbonate of soda is taken to represent 100 

 degrees of strength, so if 36 parts of any other acid liquor are 

 taken, the number of the parts of subcarbonate that it will satu- 

 rate is at once the expression of its acidimetric strength: thus 

 as a solution of 36 grains of crystallized acetic acid will saturate 

 90 grains of the subcarbonate of soda, this 90 is the expression 

 of its acidimetric strength. The acidimetric strength of an acid 

 may also be estimated from the saturation of any determinate 

 weight of subcarbonate by a determinate weight of acid : for 

 example, 100 grains of the acidum nitricum of the London 

 Pharm. ought to saturate 212 grains of subcarbonate: then as 

 100 grains of acid are to 212 grains of alkali, so are 36 grains of 

 acid representing 100 deg. of strength to the strength of the 

 nitric acid, which will be found to be 76 deg. -32 ; and in like 

 manner as 100 grains of the acidum muriaticum are required to 

 saturate 121 grains of subcarbonate of soda, its strength expressed 

 in the French mode will be found to be 44 deg. '64. 



If the strength of any acid be given in acidimetric degrees, the 

 quantity of subcarbonate of soda that any assigned weight of it 

 will saturate is thus found. As 36, the standard quantity of oil 

 of vitriol taken to represent 100 degrees of strength, is to the 

 quoted strength of the acid, so is the weight of the acid intended 

 to be used to the weight of the subcarbonate that it will saturate. 

 For instance, let it be required how much subcarbonate of soda 

 100 grains of acetic acid, from wood at 31 deg. '32, will saturate: 

 then as 36 are to 31*32 so are 100 to 87, the number of grains of 

 subcarbonate that the acid will saturate. And this is the number 

 quoted by the London college as the power of saturation that 

 their acidum aceticum fortius ought to possess. 



The use to be made of this mode of valuation may be thus 

 exhibited. Having 15001b. of rectified pyroligneous acid 8 acidi- 

 metric degrees strong, how much crystallized sulphate of soda 

 will be required to be added to the pyrolignite of lime formed 



