[ 52 ] 
Being defirous of trying the duration of colours, 
produced by aftringents, in which different quan- 
tities of pearl afhes had been diflolved ; 
EXPERIMENT V. 
In two pints of river water, I boiled one ounce 
of logwood, during ten minutes; I then added half 
ail ounce of Aleppo galls, and boiled them to- 
gether ten minutes longer ; the liquor having ftood 
to cool, was decanted off, and divided into iix 
equal quantities. N°. i remained as a ftandard* 
into N°. 2 I put fix grains of fine pearl afhes, 
"N°. 3 twelve grains, N°. 4 eighteen grains, N°. 5 
twenty-four grain's, N°. 6 thirty grains ; to fix 
drops of each of thefe liquors, I added two drops 
of a faturated folution of copperas ; N°. 2 and 3 
ftruck a deep black, N‘. 1 and 4 black, but in- 
ferior to 2 and 3, N°. 5 a brown black, N°. 6 
brown. 
From this experiment it appears, that N°. 5 and 
6 were fpoiled by an over proportion of afhes.. 
Before 1 had the pleafure of feeing your experi- 
ments, wherein you demonftrate, that a quantity 
of acid enters into the compofition ’ of ink, I 
imagined the alkali decompounded the copperas 
too.fuddenly, and difengaged the iron fafler, than 
the aftringent matter could unite with it. 
< But, mod probably, the alkali neutralized too 
great a portion of the acid.. 
All thefe writings having been now expofed fix 
months to the air, in. N°. 5 and 6 the blacknefs is 
