230 M. C. Lea on Colored Derivatives of Naphthaline. 
resists dilute acids. In diffuse light it stands tolerably, but pro- 
longed exposure to sunlight causes it to fade.* 
The production of this color does not take place unless the 
proportion of dinitronaphthaline is extremely small in compart 
son with the quantity of reducing solution, one part to one oF 
two hundred; if more is employed, the liquid assumes either a 
green, an olive, or a brown color, according to the quantity of 
the naphthaline compound. the proportion has been too 
large, the liquid, when poured into water, instead of a rich 
purple, gives a dull purple, a lilac, a lilac brown, a green or an 
olive shade, according to the degree of excess in the dinitro- 
naphthaline. A somewhat similar change in the dyeing effect 
is produced. It requires care and repeated experiment to obtain 
the exact proportions necessary for the production of the brit 
The blue solution left to itself decomposes in a few hours, att 
coming brown and muddy. The coloring power which ad 
hibits when fresh, is very remarkable. The solution obtaint 
with a few milligrammes of dinitronaphthaline, suffices to 1™ 
a rich purple color to several litres of water. 
Philadelphia, Dec. 21, 1861. | 
* The specimens of silk ibed by Mr. Lea, whit 
he has Kiully seat bs, poméns delicate shade of Mlae;parple, -Eoa | 
ee 
