GENERAL NOTES. 131 
In making and using carminic acid pure alcohol and distilled 
water give the best results, because a portion of the carminic 
acid is converted to carminates by the salts of impure water. In 
making alcoholic ammonic carminate this precaution is not as 
necessary, because the color of the carminates produced by the 
impurities of the water is so nearly like that of ammonic carmi- 
nate. Alcoholic carminic acid may be used as Grenacher’s car- 
min solution is used, to color sections from which the coloration 
is to be afterwards partly extracted by very dilute hydrochloric 
acid, leaving nuclei red. Another way to use carmin solutions, 
which is specially applicable to alcoholic carminic acid, is to pre- 
cipitate the carmin in the tissues by some salt, the carminate of 
the base of which gives a desired coloration. I have found, for 
example, that specimens hardened for a moment under the cover 
glass with an alcoholic solution of corrosive sublimate (mercuric 
chloride) and, after washing with alcohol, colored in alcoholic 
carminic acid, took a fine coloration of mercuric carminate. 
So, too, specimens colored in alcoholic carminic acid can 
be changed by a few moments’ treatment with a very dilute 
alcoholic solution of lead-acetate or cobalt nitrate to a 
beautiful purple. With lead-acetate used as above a double 
coloration is sometimes produced, but I have not examined suf- 
ficiently these colorations to accurately describe them. Cupric 
and other salts, used as above described, have not given me very 
favourable results. Sometimes salts in the tissues of the animals 
themselves change portions of the carminic acid to purple car- 
minates, giving a double coloration without further treatment. 
Picric acid added to alcoholic carminic acid in extremely 
small quantities (best in a dilute alcoholic solution, testing the 
solution on specimens after each addition), makes a double alco- 
holic coloring fluid (a so-called picro-carmin). I have been un- 
able thus far to determine the proportion of picric acid required 
for this solution, having in every case added an excess, All 
different kinds of carmin solutions can be made from carminic 
acid with the advantage of having always uniform strength, of 
being definite mixtures, and of not spoiling as readily as those 
made directly from cochineal. Incompatible reagents with car- 
minic acid are, of course, all alkaline solutions, and nearly all 
metallic salts ; with ammonic carminate, are naturally all acids ; 
with all carmin solutions, are bromine and chlorine. 
I hope later to try some coloring experiments with coccinin, 
ruficoccin, carmin red, and ruficarmin, all of which are derived 
from carminic acid, and of possible value to the histologist—Geo, 
Dimmock, in“ The American Naturalist” for March, 1884. 
