Chemical Science. 395 



Substance. Benelius's Notation. Whewell's Notation. 



Phosphate of Lime C 8 P a 3 C + 2 P 



Felspar . . KS 8 + 3 A S 8 (K + 3 S) + 3 (A + 3 S) 



Alum KS 8 + 2 AS a + 48 Aq 2 (A + 3 S) + K + 2S + 48 : A?. 

 Coefficients are, in all cases, used instead of indices. 



23. PARA-TARTARIC ACID. 



M. Dulong read to the academy a letter from M. Berzelius, relative 

 to numerous chemical compounds, which being similar in the nature 

 and proportion of their elements, yet differ in property from each 

 other. M. Berzelius had been particularly engaged with the acid 

 found in tartar by M. Gay Lussac, which has been called Vosges 

 acid (Thannic acid.) He shows that this acid, though differing from 

 ordinary tartaric acid in many properties, has exactly the same com- 

 position. 



Similar difference in properties without difference of composition 

 is found in phosphoric and pyro-phosphoric acid ; in stannic acid or 

 deutoxide of tin, obtained from tin by nitric acid, or obtained from 

 Libavius liquor by precipitation. 



To associate and yet distinguish substances under tliese peculiar 

 circumstances, M. Berzelius proposes to prefix the Greek term para 

 to the name of that body which occurs most rarely, or which is 

 obtained with the most difficulty, thus: Phosphoric acid, and para- 

 phosphoric acid ; tartaric acid, and para-tartaric acid ; stannic acid, 

 and para- stannic acid, &c.* 



24. PREPARATION OF PIPERIN, BY MR. CLEMSON. 



The pepper should be ground and digested in alcohol of specific 

 gravity 0.832, or 0.817 at a smart distilling heat; an alembic, with its 

 water bath, is at once convenient and economical; the whole should 

 be agitated from time to time, and the fluid changed if necessary. I 

 know of no better indication of the entire extraction of the piperin, 

 than the want of taste in the marc or insoluble residue ; although 

 acridity (as has been represented) is by no means a property of piperin. 

 The alcoholic solutions being united, should be reduced over a water 

 bath. The distillation ended, there will be found in the bottom of the 

 alembic a deposit composed of a great deal of piperin, and a black 

 acrid resino-oleaginous substance ; the separation of this latter com- 

 pound from the piperin is difficult in the extreme ; so much so, that 

 I have seldom or never seen the preparation free from acridity, which 

 not only destroys, but produces a contrary effect to that desired, 

 when employed as a remedy. The greater part of this viscous oil 

 may be separated by cold alcohol, piperin being much less soluble in 



* Jour, de Pharmacie, 1830, p, 622. 



