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considerable quantity of oxalate of lime results, and if this 
filtrate be rendered neutral by ammonia and acetate of lead be 
added, a precipitate of a beautiful bluish purple ensues. 
(7) If the precipitated carmine be collected, washed with 
a little cold water, (it is soluble in excess of boiling water) and 
again dissolved in liquor ammoniz, and to the solution acetate 
of lead be added in sufficient quantity, a precipitate of a reddish 
purple or purplish red is obtained. 
(8) This precipitate may now be carefully washed and 
mixed with water ; the quantity obtaied from about 100 grains 
of ordinary carmine may be mixed with about 4 ounces of rain- 
water, and decomposed by sulphuretted hydrogen gas. This 
operation requires great care, as the peculiar colouring principle 
or acid, and which I shall call coccineo-carminic acid, and which 
is here combined with the oxide of lead, is easily decomposed, 
and partly converted into another acid, the purpwreo-carminic 
acid, the same as that combined with the lead in (6). 
It is best to operate with a small apparatus composed of two 
six ounce bottles, containing one the sulphide of iron, and the 
other the creamy mixture of the coccineo carminate or, for short, 
c. carminate of lead. A tube 4+ inch thick externally is wide 
enough for the tube through which the gas passes, the bubbles 
of gas should not come through faster than about 3 in a second, 
and the operation should be arrested at the end of about 10 
minutes or a quarter of an hour at most ; any way, the operation 
must be arrested before the whole of the lead is saturated, and 
some of the c. carminate of lead must be reserved apart to mix 
with that in the bottle at the end of the operation to absorb 
any sulphuretted hydrogen that may be dissolved in the liquor. 
I fancied that the operation succeeded better when the air 
was excluded as much as possible from the bottle containing the 
ce. carminate of lead, by means of a little blotting paper loosely 
stuffed in at the neck. 
When the operation is finished, and after the contents of the 
