on the Ammonia-cobalt Bases. 237 
terminal syllable “iaque,” employed by Frémy, not merely be- 
cause it is not an English termination, but because by omitting 
it we obtain shorter and more convenient words. Thus, we say 
obalt and Luteocobalt, instead of Roseo-cobaltiaque and 
Luteo-cobaltique, or Roseo-cobaltia and Luteo-cobaltia, which 
are the English equivalents. The shorter names, as will here: 
after appear, also agree better with our own theoretical views, 
since we consider the compounds in question conjugate metals 
and not ammonias. 
With the view of making the description of our salts as com- 
_ as possible, we have followed the excellent example of 
rémy, and referred the colors of these substances to Chevreul’s 
chromatic scale. Frémy had the advantage of Chevreul’s own 
determinations. We have employed, for the purpose, the chro- 
matic scales recently published in Paris y Digeon, and which 
appear to be reliable; in any event they give some precision to 
determinations of color. As we have found that very a of 
the salts of the ammonia-cobalt bases exhibit a well marked di- 
chroism, we have in most cases examined the light reflected from 
layers of crystals, by Haidinger’s dichroscopic lens, and have 
£1ven the colors of the ordinary and extraordinary images as ob- 
tained in this way. Asa curious physical result, we may here 
mention that, in general, the cobalt color predominates in the or- 
nary image. ae. 
We are indebted to Prof, Dana for the determination of the 
systems to which many of our crystals belong, and of their prin- 
“pal forms, as well as for our figures, and embrace thi we mn 
nity of expressing our grateful acknowledgement of his valuable 
assistance. 3 
METHODS OF ANALYSIS. : 
The accurate quantitative determination of the different ele- 
ments which enter into the constitution of the ammonia-cobalt 
bases and their salts, is attended with great difficulties. We 
Cobalt—The determination of the cobalt in these salts may, 
2 most cases, be very easily and accurately effected by the fol- 
-Owing process, A weighed portion of the salt is gently heated 
in a deep platinum crucible, with a quantity of pure and strong 
sulphuric acid sufficient to moisten the whole mass. Some a 
vescence is generally produced by the addition of the acid, but 
there is no danger of loss if the crucible be sufi y large, 
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