Page:Popular Science Monthly Volume 90.djvu/891

 Popular Science Monthly

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��have no little trouble in trying to match colors, whether silks or house paints; not because the chemist cannot make the same shade twice. Indeed the synthesis of dyes is like the multiplication table for reli- ability. It always gives the same result.

The Modern Chemist Experi- ments on Paper

Instead of messing around in a laboratory with a dozen or more retorts, a lot of stains and a dirty, smudg>' atmosphere, the chemist of today simply sits at his desk, far away from the choking acid fumes of his laboratory, and figures out on a sheet of paper the colors he wishes to produce. He knows that certain in- gredients will yield certain results and pro- ceeds to combine them in such a way as to build up what he wants before he ever carries out the actual chemi- cal reactions theoreti- cally worked out.

Such a procedure forms a remarkable contrast with the laborious experi- menting which led to the discovery of mauve, the first coal tar dye, by Perkin, in 1856. He was an en- thusiastic young English chemist who took a notion

to build up quinine from simpler chemicals. He chose a college Easter vacation for his research work and labored day and night to obtain his ends. But quinine did not result; only a dingy dark precipitate was formed. Perkin was disgusted. The stuff would not even dissolve in water. He tried alcohol. To his astonishment and delight, a most beautiful violet color was produced which dyed silk a magnificent purple.

Though only eighteen years of age, Perkin was old enough to realize the vast commercial possibilities of this discovery. Within three years the women of England had lost all sense of reason over the new

��cok

��Punch made the following comment :

"Lovely woman is just now afflicted with a malady- which apparently is spreading to so serious an extent that it is high time to consider by what means it may be checked. . . . One of the first symptoms by which the malady declares itself consists in the eruption of a measly rash of ribbons about the head and neck of the person who has

caught it. The erup-

��Hair fastened with glue from all day suckers

Cheek colored wHh poisonous dye from candy

Waist dyedv/rth coloring matter from lollypops

���tion, which is of a mauve color, soon spreads, until, in many cases, the suf- ferer becomes com- pletely covered with it."

��5kirt dyed another^ color also from ollypops

��A poisonous lollypop

��Dyed vivid areen from a cenrs worth of lollypops

��^Plated -j ■'with copper' \^ from can of peas

��Professor D. R. Hodgdon dyed this doll's brightly- colored clothes with coal tar coloring-matter which he obtained from cheap, poisonous candy

��In speaking of finished dyes, we ha\e jumped from coal clean over the thou- sand and one in- tervening pro- cesses, to the usable product. After coal is first split up, the next most important way station on our trip from coal to the outskirts of the whole in- dustn,, is coal tar.

Coal tar is the most disagree- able, foul-smell- ing, black sticky liquid you ever saw.

When gas is distilled coal tar condenses in the pipes. For years e\'ery gas works had to contend with it as an extremely bothersome by-product. It was worse than waste, for vegetation died wherever it was spilled; streams were polluted if it was allowed to drain into them. It is a com- bination of liquid and solid substances consisting mainly of hydrocarbons, which are complex compounds of hydrogen and carbon. The separation of these constitu- ents into such products as paraffin, naph- tha, benzene, cyanogen and the like, is now an industry netting millions of dollars annually. Coal tar is now practically dis- tilled in order to obtain these products.

Fractional distillation is the gradual rais- ing of the temperature, driving off the

��«5hoe lined with shellac from peach pits

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