402 Prof. A. De la Rive's Researches on the Magnetic 



Sulphuric Acid. 



Of all liquids sulphuric acid is that which, in the experiments, 

 presented the greatest difficulty. The cause of this was twofold : 

 — first, the difficulty of procuring sulphuric acid quite pure and 

 concentrated; secondly, the facility with which the concentrated 

 acid absorbs humidity from the air — an absorption which, by 

 altering it, modifies singularly its magneto-rotatory power. 



Three series of experiments, made upon some sulphuric acid 

 procured from a vendor of chemicals at Geneva, gave : — 



Sulphuric acid. Water. Ratio. 



8 



9 50 



0-814 



7 55 



9 45 



0-812 



9 



11 



0-818 



Mean . . 0-8147 



Subsequently some sulphuric acid from the works of M. 

 Rousseau, of Paris, gave, in three series of experiments, the fol- 

 lowing results : — 



Sulphuric acid. Water. Ratio. 



7 50 9 40 0-810 



7 20 9 15 0-792 



7 20 9 13 0-796 



Mean . . 0-799 



For this number 0*800 may be substituted without sensible 

 error, to express the specific magneto-rotatory power of the Paris 

 sulphuric acid. It afterwards served for the calculation of the 

 results I obtained by operating on mixtures, in various propor- 

 tions, of the same acid and water. 



The following is the last series of observations made upon this 

 acid : — 



Acid. Water. 



16 35 



9 15 



7 20 



17 30 8 20 



9 10 



16 30 



9 15 



7 15 



17 40 8 20 



9 20 



16 45 



9 15 



7 30 



17 35 8 20 



9 15 



16 40 



9 20 



7 20 



17 30 8 20 



9 10 



16 40 



9 20 



7 20 



Mean rotation 



. 9 13 



16 40 



9 20 



7 20 







16 40 



9 20 



7 20 







Mean 



rotation ■ 



, 7 20 







The ratio of 7° 20' to 9° 13' is 0-796, which represents the 

 specific magneto-rotatory power of sulphuric acid given by this 

 series. 



