The times., 1900-12-30

! and so on. By means of conceptions such
| as these many interesting compounds
| have been built up out OF the elements
which they contain; e. g., urea and uric
| acid, constituents of urine; theo-bromine
/ and caffeine, the essential principles of
Cocoa and tea; alizarine and indigo, val
liable dye stuffs; and several of the aka
| loids, bitter principles contained in plants,
| of great medicinal value.
They have led, too, to the discovery of
many brilliant colors, now almost uni
versally employed, to the exclusion OF
those less brilliant, because less pure.
| derived from plants, and in one or two
cases from animals; the manufacture OF
! gun cotton, dynamite, and similar high
explosives; and to the development of the
! candle industry, the sugar manufacture
! to Improvement in tanning, in brewing,
and in the preparation of gas and oils for
| Illuminating purposes. In short, it may be
said that the industrial progress of the
| latter half of the century has been due to
| the theoretical views of which a short
sketch has just been given.
| Such formulae, however, can evidently
not represent the true constitution of mat
| ter, inasnuch as the atoms are imagined
to lie on plane, whereas it is evident
that they must occupy space OF three di-
mensions and possess the attributes of
solidity. The conception which led to the
formulation of such views was due first to
Pasteur, in his later years director of the
institute known by his name at Paris, and
more directly to LeBel, and van Z Hoff,
now professor at Berlin. independently of
otb Tn
that it was possible to separate the tive
varieties of tartaric acid from each other,
and that that one which rotated the plane
of polarized light to the right gave crys-
tails with an extra face, unsymmetricaDy
disposed with regard to the other faces of
the crystal The variety, the solution OF
which in water was capable of producing
left-handed rotation. also possessed SINH
lar face. but so placed that it's reflection
in a mirror reproduced the right-handed
variety. Pasteur also showed that a mix
ture of these acids gave crystals not char
acterized by an uusymmetrically placed
face; and also that the solution was with
out action on polarized light These OBJ
servatiOns remained unexplained until LIE
Bel and van { Hoff, in 1874. simultaneous
ly and independently devised a theory
which has up till now stood the test of re-
search. 1t is briefly this: Imagine two
regular tetrahedra, or three-sided pyra-
mids, standing each on its triangular base.
An idea can best be got by model, easily
made by laying on table three lucifer
matches so as to form an equilateral tri-
angle, and erecting a tripod with three
other matches, so that each leg of the
tripod stands on one corner of the tri.
angle. At the centre of such a tetrahe-
dron, an atom of carbon is supposed to
be placed. Marsh gas. CHI. is supposed to
have such structure, each corner. or
solid angle of the structure (of which
there are four being occupied by an atom
of hydrogen. This represents the solid or
stereochemical formula of methane, or
marsh gas. Now suppose one OF the atoms
Of hydrogen in each of these structures to
be replaced by chlorine the group (OH).