PRESIDENTIAL ADDRESS. 441 
As an investigator of vegetable colouring-matters, no one has been more 
assiduous or has displayed greater skill of late years than A. G. Perkin. 
His recent refined investigation of the colour-yielding constituents of the 
indigo plant is of exceptional value at the present time, although it is to be 
feared that it comes too late to save the situation in India. The work of the 
brothers Perkin, it may be pointed out, is of exceptional interest on the 
human side as well as from the scientific standpoint, as their enthusiasm 
and wonderful manipulative skill afford a striking and noteworthy example 
of hereditary genius. 
Two substances of commanding interest which have long resisted attack 
—the red colouring-matter of the blood and leaf-green—are at last going the 
way of all things chemical, as the secret of their nature is being wrung from 
them. In Willstatter’s skilful hands chlorophyll is proving to be by no 
means the fugitive material it was supposed to be; the complexity of the 
problem it offers, however, seems to be far beyond anything that could have 
been anticipated ; so much greater will be the interest attaching to the final 
solution. The discovery that green chlorophyll is a magnesium salt is of 
special importance, as the first clear indication of the manner in which 
magnesium salts are of service to plants. 
Apart from the special interest which attaches to the investigation of 
vegetable colouring-matters on account of their being coloured substances, 
such inquiries are of value as furnishing material for the discussion of the 
metabolic activity of plants.* 
Even colloids are being brought into line. Studded as they are with 
active centres (oxygen or nitrogen atoms), they seem to be able to attract 
and retain hydrone molecules at their surfaces in ways which give them 
their peculiar glue-like attributes: as a consequence living tissue appears 
to be little short of animated water. 
To the present generation of students, the organo-metallic compounds 
must have appeared to belong to the past; the discovery of methides of 
platinum and gold by Pope will not only serve to reawaken interest in this 
group of compounds, but is of primary importance as a contribution to our 
knowledge of the valency of these elements; the stability of the platinum 
derivatives is altogether astonishing. 
The discovery announced in June last, at the International Congress of 
Chemistry, by Mond of compounds of carbonic oxide with ruthenium and 
uranium is a striking and most welcome extension of his previous labours, 
which had placed us in possession of carbonyls of nickel, iron, and cobalt. 
* But a note of sadness pervades the story. The effect of learning to under- 
stand Nature always appears to be that we at once brush her aside when we have 
wrested from her the secrets which she has so long preserved inviolate. No sooner 
did we learn the nature of the madder colouring-matters than we proceeded to 
prepare them artificially—thus putting an end to the cultivation of a valuable crop. 
Indigo is meeting with a like fate, a catastrophe which might well have been 
avoided had scientific assistance been called in at the proper time. Not content 
with making natural colouring-matters, we set to work to outrival the rainbow in 
our laboratories ; the feminine world is decked with every variety of colour in 
consequence, although unfortunately our blends too often lack the beauty of those 
of truly natural origin, which rarely, if ever, offend the eye. We congratulate 
ourselves on our cleverness in thus imitating Nature but no idea of thrift possesses 
us + moreover, our attempts to imitate if not to undo her work are never direct 
but are always made with her aid, with Nature’s product—coal ; we are no longer 
content to ride on horseback but must rush through space, and instead of 
watching the birds fly seek to emulate them but always with the aid of fuel won 
by Nature from the soil and air in days long past. Too much is being done in 
every direction to waste natural resources, too little to conserve them, too little to 
employ man in his proper place—as tiller of the soil. Here lies the chemist’s 
opportunity. At no very distant date, perhaps, when petrol is exhausted, toll 
will be taken from the sun in the form of starch or sugar and this will he converted 
into alcohol, 
