-and Notice of a new analytical Scale of Equivalents. 429 



Thomson and Ure agree in assigning 2 atoms of water to 

 1 of acid ; but the latter reduces the atomic weight to 8*375 

 (Diet., 2nd edit., Appendix, 84) ; the latter raises it to 9*5; 

 pointing out however, in a note, its variance from his own 

 analysis. (First Principles, i. 123, note.) 



The apparent facility of determining the atomic weight of 

 these crystals would lead us to impute the differences above 

 quoted, to inconstancy in their water of crystallization. But 

 having generally found this equivalent between 8*77 and 9", 



I suppose the ordinary constitution to be Acid 1 ... 7*27 



Water l^ ... 1*6875 



And assume the equivalent 8*96. 8"9575 



(«'.) Columbic. — See the note on Columbium. 

 (k.) Ferro-prussic. — Of the discordant data relating to the 

 atomic weight of this acid, an experiment of Dr. Ure's (Diet., 

 2nd edit., Appendix, 805) seemed the most direct; but subject 

 to the uncertainty of all atomic deductions from precipitation 

 with salts of lead, excess of which is apt to fall with the pre- 

 cipitate, as was observed some years since by Berzelius. 



Some experiments of mine, guided by Mr. Porrett, give 

 13*28 for the atom of ferro-prussiate of potash; constituted as 



follow: Potassium 4*95 = 1 atom. 



Oxygen..., 1*5 == 1| atom. 



Hydrogen 0*19 = 1| atom. 



Cyanogen 4'92 = l^atom. 



Iron 1*72 = ^ atom. 



13*28 



If this be, as I believe, anhydrous ferro-prussiate of potash, 

 the acid is 7*33 : but it may be construed in other ways ; and 

 there is an anomaly about the half atoms, which becomes still 

 more perplexing in prussian blue, composed of 1^ atom of 

 acid to 1 atom of red oxide of iron, or rather of 3 atoms of 

 acid to a double atom of oxide. I had therefore some hesi- 

 tation in putting the dry acid on the scale, where it is accom- 

 panied with a ? The composition of the crystallized acid I 

 have not ascertained : that of the salts corresponds in analysis 

 (though differing in theory) with the previous determinations 

 of Berzelius. 



(/.) Nitrous. — It is almost superfluous to remark, that the 

 nitrous acid of Berzelius is the hyponitrous of English che- 

 mists. 



(?n.) Oxalic. — See the note on Benzoic Acid (d). The cr}-- 

 stals found by Thomson to contain 4 atoms of water (First 

 Princ.) having occurred to no one else, seem to be the result 



of 



