TRANSACTIONS OF SECTION B. 783 
influence of mordants was observed to vary with different colouring-principles. 
Some, for example, those of alizarin, anthrapurin, flavopurpurin, nitro-alizarin, 
ecerulein, alizarin blue, carminic acid, and others, give fast colours with all the 
usual mordants (Cr, Al, Sn, Cu, Fe) ; others, e.g. heematein, give comparatively fast 
colours with Cr, Ou, Fe, and fugitive colours with Al and Sn; and others, again, e.g. 
fisetin, give fugitive colours with all mordants. With respect to colouring-matters 
not requiring the aid of mordants, they are found to comprise both fugitive and fast 
dyes, their behaviour differing, apparently, according to their chemical constitution. 
A comparison made between the natural and artificial colouring-matters showed 
that we have at the present time a total of about three times as many fast coal-tar 
colours as we have of fast natural dye-stuffs. Of the three hundred or so of 
distinct coal-tar colouring-matters, thirty give extremely fast colours, and an equal 
number or more give medium fast colours; whereas of the thirty natural dye-stuffs 
usually employed, only about ten may be reckoned as giving fast colours. 
The general conclusion arrived at was that, if it were necessary or desirable, the 
modern textile colourist could, even now, dispense entirely with the natural dye- 
stuffs, and that, too, without any detriment to the permanency of his productions. 
Great stress was laid upon the necessity of employing the coal-tar colours aright, 
with discretion and intelligence, suiting the colouring-matter to the fabric and its 
ulterior use, whereby the evil repute into which they have fallen in many places 
would be entirely removed. 
8. Notes on the Limits of the Reactions for the Detection of Hydrogen Diowide, 
and the Reactions for Uranium. By T. Farruny, F.R.S.E. 
The results as regards very dilute solutions show :— 
1, That on the addition of a dilute solution of uranium nitrate to one of hydro- 
gen dioxide, it is preferable not to have an excess of hydrogen dioxide, 
2. That a distinct precipitate is obtained on allowing a solution of 0-002 per 
cent. hydrogen dioxide to stand for two hours with excess of uranium nitrate. 
3. That it is doubtful if less than 0-005 per cent. of hydrogen dioxide can be 
detected by the chromic acid and ether test. 
4, That the limit of uranium which potassium ferrocyanide can detect is about 
0:005 per cent. (very faint). 
5. That the limit of uranium which hydrogen dioxide can detect is about 
0-015 per cent. 
Further, as regards the actual quantities detected, working with 5 c.c. of the 
solution in each case :— 
2. 00001 grammes of hydrogen peroxide gave a precipitate with excess of 
uranium in two hours. 
3. It is doubtful if less than 000025 grammes of hydrogen dioxide can be 
detected by the chromic acid and ether test in such dilute solutions as the above. 
4, The limiting quantity of uranium which potassium ferrocyanide detected was 
0:00025 grammes. 
5. The limiting quantity of uranium which hydrogen dioxide detected was 
0:00025 grammes. 
WEDNESDAY, SEPTEMBER 10. 
The following Papers were read :— 
1. On Veratrin, and on the Existence of Two Isomeric B-Picolines. 
By Dr. F. AwRENS. 
The experiments of Wright and of Bosetti on the action of alkalies were re- 
peated and extended. It was found that when veratrin is treated with potash or 
with baryta water, or when it is heated to 200° C. with ammonia or distilled 
water, it is decomposed into angelic acid and a basic substance of the composition 
C,,H,,NO,. 
