\9Si Dr. Thomas Thomson [Aug. 



need not be here stated. I put more dependence upon the 

 following' synthetical experiment than upon any of the 

 analytical ones that I made, because it is susceptible of 

 greater precision than any of them. Indeed, I consider it 

 as approaching as near the truth as it is possible to do by 

 our present methods. 



5. 86*76 grs. of pure fused carbonate of potash were 

 dissolved in water, and to the solution 102 grs. of crystals 

 of racemic acid were added by degrees till they were com- 

 pletely dissolved. The liquid was found still to contain an ex- 

 cess of potash ; for it rendered cudbear paper violet. After 

 adding 4*34 grs. of racemic acid, (previously dissolved in 

 water) and agitating the mixture well, it was found still to 

 render cudbear paper violet. This led me to suspect that 

 cudbear paper is not capable of determining the exact point 

 of saturation of carbonate of potash by racemic acid. The 

 whole liquor was put into a platinum basin and evaporated 

 down till it amounted only to IJ cubic inch. It was still 

 liquid, and perfectly transparent, and still acted on cudbear 

 paper like an alkali. 1*1 grs. of racemic acid was added, 

 the liquid was gently heated and set aside. It soon became 

 muddy, and deposited a quantity of bi-racemate of potash, 

 which, after being separated and dried, weighed (including 

 the small quantity still left in solution) 3.3 grs. 



Now, 3*3 grs. of bi-racemate of potash contain 2*42 grs. 

 of racemic acid, the half of which must be the amount of 

 the excess of racemic acid added to the carbonate of potash, 

 over and above what was necessary to neutralize it. But 

 1*21 grs. of real racemic acid, to bring them to the state of 

 the crystals, require to be combined with 0*359 grs. of 

 water. This makes 1*569 grs., which, when subtracted 

 from 107*44, leaves 105*871 grs. of the crystals of racemic ■ 

 acid, as the quantity which neutralized 86*76 grs. of carbo- 

 nate of potash. 



105*871 grs. of crystals, when deprived of their mechani- 

 cally mixed water, would be reduced to 103*913 grs. From 

 the preceding analysis of these crystals it follows that they 

 are composed of 



Real acid 81*544 



Water 22*369 



103*913 



