April 26, 1873.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
845 
work has rather extended in the direction of the methyl 
gums, 
Without further preface, I may state that the object of 
this note is 11 to announce the fact that these gums furnish 
a large quantity of methyl-aniline by destructive distilla¬ 
tion. After the Hofmann gum has been kept fused for 
some time to chive off nearly the whole of the enclosed 
water, it is charged into an iron still, either with or with¬ 
out the addition of roughly powdered charcoal, and then 
submitted to a greater heat over a coke fire.* An oily 
body of nauseous odour soon commences to come over, and 
the distillation may be safely carried on until the product 
amounts to half the weight of the gum originally em¬ 
ployed. Small quantities of water and ammonia com¬ 
monly appear, together with a little permanent gas ; but 
practically the oil and residual pitch may be said to be 
the sole resultants of the operation. This oily body is 
methyl-aniline, and when purified by rectification in glass 
retorts becomes nearly colourless, boiling at 200° C., and 
rising only a few degrees above that point towards the 
end of the distillation. Not only does it possess the pe¬ 
culiar odour so characteristic of methyl-aniline, but the oil 
has the required boiling-point as stated above, and the 
remarkable property of forming permanently liquid com¬ 
pounds (not crystallizable) with any of the ordinary acids. 
When acted upon with arsenic acid, at or near the boiling- 
point of the mixture, it furnishes a violet of somewhat red 
shade, which may be employed as a dye; and the oil gives 
colours of various tints when treated with other oxidizing 
agents, according to the usual reactions of methyl-aniline. 
The red-violet from the arsenical melt may, after purifica¬ 
tion, be converted into the bluer shades by the Hofmann 
process, when a new generation of gum is again observed. 
The specific gravity of the methyl-aniline oil has varied 
a little in different operations, but keeps within the ranges 
of 0’95 and 0 - 97. It is probable that this trifling varia¬ 
tion may be ascribed to admixtures of dimethyl-aniline, 
due in part to the introduction of higher methylated pro¬ 
ducts into the crude gum employed in these experiments. 
By operating in a similar manner upon the ethyl gums 
the corresponding ethyl-aniline has been obtained, the 
boiling-point of which was higher and not so definite 
(205°-210 Q C.) as in the case of the oil already described. 
By way of conclusion, and as giving further proof 
towards establishing the identity of the new oils with 
ethyl- and methyl-aniline respectively, it may be stated 
that they fail to give Girard’s blue when heated with 
rosolic acid or rosaniline, but take the peculiar course of 
changing slightly towards violet, and then suddenly be¬ 
coming decolourized, — reactions almost without parallel 
in the history of the tinctorial aniline derivatives. 
PROFESSOR TYNDALL ON LIGET.+ 
{Continued from p. 830.) 
The question which we have now to answer experi¬ 
mentally is this : Is the eye as an organ of vision 
commensurate with the entire range of solar radiation ? 
Is it capable of receiving visual impressions from all 
the rays emitted by the sun ? The answer to this 
question we find to be “ No.” On both sides of the 
spectrum there is a copious outflow of rays which are 
incompetent to excite vision. Beyond the violet end of 
the spectrum this vast efflux of rays, entirely useless as 
regards our present powers of vision, is so copious and 
varied as to be able to form an invisible spectrum five ©r 
six times as long as the visible one. If the theory of 
* A mixture of pulverized iron borings, kaolin, and 
syrupy silicate of soda forms an excellent lute for fixing on 
the head of the still, as it withstands a high temperature 
without softening. 
t Abstract of a series of lectures delivered in the Cooper 
Institute, New York, and reported in the New York 
Tribune . 
evolution be true, then there are in store for man visual 
inspections far grander than he has yet experienced. 
These eyes of the future should find beyond the violet 
the actinic rays which produce chemical effects, rays 
which produce the decomposition of carbonic acid in 
plants, and which have so great a power in all the 
processes of vegetable and animal life. 
These ultra-violet rays or waves, though incompetent 
to stir the optic nerve to vision, are able to agitate the 
molecules of certain substances so as to shake them 
asunder and produce chemical decomposition. All pho¬ 
tography is founded upon such chemical actions ; but 
there are special substances on which these ultra-violet 
rays exert a special power. They darken the white salts 
of silver ; and, by permitting a spectrum to fall on paper 
properly saturated with a solution of such salts, the 
chemical action reveals the existence and the extent of 
the ultra-violet spectrum. One of the earliest, if not the 
very earliest attempts of this character was made by the 
celebrated Thomas Young, who photographed in this way 
the rings of Newton ; thus proving that these invisible 
rays obeyed the principle of interference exactly like the 
visible ones. 
As a general rule, bodies either allow the passage of 
light or they generate it. To use technical terms, they 
transmit the light or they absorb it, reducing it to dark¬ 
ness. This absorption, however, is not annihilation of 
the light; it is, in fact, a conversion of it into heat. But 
there is a third case in which the light is neither absorbed 
nor reduced to darkness, but tia isformed into light of 
another kind. Now, Professor Stokes, who has long 
occupied the chair of Newton in the University of 
Cambridge, and who is one of those original workers, 
who, though not widely known beyond scientific circles, 
really constitute the core of science, has demonstrated 
this change of one kind of light into another, and 
has pushed his experiments so far as to render the in¬ 
visible rays visible. A piece of paper moistened with 
sulphate of quinine, when introduced into the portion of 
the spectrum beyond the violet, renders the non-luminous 
rays which lie there luminous. By the use of violet 
glass in cutting off the great mass of the luminous rays, 
we obtain a light rich in these invisible rays, and this 
light may be thrown upon the screen and the presence of 
such rays demonstrated by the paper covered with 
sulphate of quinine. 
[A sheet of paper, moistened with sulphate of quinine, 
was introduced into the spectrum beyond the violet. Im¬ 
mediately a bluish tint appeared where previously none 
had been. The light from the electric lamp was then 
suffered to pass through a sheet of violet-coloured glass, 
and the experiment was repeated with the spectrum thus 
obtained. By the use of another sheet of paper a beauti¬ 
ful green hue was produced. A sheet of paper properly 
prepared, on which a rose with leaves appeared in outline, 
was placed in this light, and immediately the rose as¬ 
sumed a delicate blue tint, while the leaves showed an 
exquisite emerald green.] 
These effects are due to the quality possessed by the 
sulphate of quinine and by other bodies, of changing the 
rapid vibrations of the rays beyond the violet into slower 
vibrations, and thus rendering the non-luminous rays lu¬ 
minous, and also changing one kind of light into another. 
Fluorescence is the name given to these effects. The 
human eye is a beautiful instance of this fluorescence, as 
Dr. Bence Jones has shown ; and there is, no doubt, some 
substance in the crystalline lens analogous to the sulphate 
of quinine in its action. 
The next question before us is, is radiation capable of 
diffusing heat ? The same apparatus with which the dif¬ 
fusion of light has been shown will also serve to show the 
diffusion of radiant heat. I first cause an image of the 
carbon points to fall on the screen. By drawing out the 
lens the image contracts, but its intensity increases. If 
now I place some paper in the focus of the image formed 
the paper will smoke. 
