6S0 



Messrs. Playfair and Joule on 



Theoretical. By Kopp's* By our Mean of 



sp. gr. experiments, experiments, experiments. 

 Potash alum . 1-727 ... 1-724 ... 1-726 ... 1-725 

 Chrome alum 1-833 ... 1-848 ... 1-826 ... 1-837 



The number 1 1 must then be very near the truth, if it be 

 not absolutely the truth. We now append an equally severe 

 test for our view that the volumes of many salts are multiples 

 of 9*8, the number representing the volume of ice. If there 

 be an error in this number, it must become very notable in 

 the phosphates and arseniates, when multiplied by 24, or in 

 carbonate of soda when multiplied by 10. Perhaps sugar 

 itself will form as severe a test as could be desired, for we pro- 

 ceed on the extraordinary fact that the 12 atoms of carbon in 

 sugar have ceased to occupy space, and that the bulk of an 

 atom of sugar is just the bulk of Hn On, or its 11 atoms of 

 hydrogen and oxygen, quasi water, frozen into ice. 



Theoretical 

 sp. gr. 



Carbonate of soda . 1-463 

 Phosphate of soda . 1-527 

 Subphosphate of soda 1-622 

 Arseniate of soda . 1-713 

 Subarseniate of soda 1-808 

 Cane-sugar . . .1-591 



Sp. gr. ac- 

 cording to 

 our expe- 

 riments. 



1-454 

 1-525 

 1-622 

 1-736 

 1-804 

 1-596 



other 

 author- 

 ities. 



1-423 Haidinger. 



1*514 Tiinnermam j . q 



none ,;[ ^rH 



1-759 Thomso%p yin 



none 



1-600 Schiibler & Renz. 



Thus even in salts so difficult to obtain in a proper degree 

 of hydration free from mechanical water, as those given in the 

 above table, the difference between the theoretical and experi- 

 mental numbers is not greater than might have been expected. 



We give one other class of salts to illustrate position c in 

 Prop. II., there being in these salts a certain number of vo- 

 lumes represented by 11, and a certain number by 9-8, CuO, 

 SOg representing the number of volumes with the divisor 11. 



Theoretical Sp. gr. by our Sp. gr. by other 

 sp. gr. experiments. authorities. 



. 2-270 2-254 2-274 Kopp. 



. 1-926 1*931 1-912 Hassenfratz. 



, 1-854 1-857 l-MO Idem. 



1-660 1-660 1-660 Idem. 



2-033 ... 2-037 Kopp. 



Stdpnate of copper 



««^'=.*. zinc . 



i1nni,rj|i- 



iron , , 

 magnesia 

 nickel 



We have selected these three classes of salts as being the 

 most severe tests which we could apply to our theory, and 

 any chemist who has had experience in this subject will at 

 once admit that the theoretical and experimental numbers are 



* Jiinalen der Pharmacie, Bd. xxxvi. S. 10. 



