By FREDERICK DANJEI, CHATTAWAY.

CASES of triniorphic change, although several have been observed, are sufficiently rare f o r a ne~7 one t o bet of interest. The pheno- menon is well shown by 4-nitroaceto+o-toluidide, which on crystal- lisation undergoes two successive t~ransformations before a stable state is reached.

By nitrating o-toluidino in the presence of excess of concentrated s r ~ l p h ~ ~ ~ * i c acid, Niiltiiig and CJollini (Nrr.., 1884, 17, 269) first p e - J ) ; A I W ~ the base, atict by heating with acetic arthyclritle couverted i t ixito t he acetyl derivative. This they describe very briefly as c.~-ysi,allisiiig iu yellowish-white iieeclles melting at 150 -1Gl0.

Speaking in general terms, all aiiilides crystallise in one of three easily recogiiisable forins, namely, a slender prismatic form, a compact form, and a hair-like form, and many have been obtained in two od them.

4-Nitroaceto-o-toluidide can be, obtained in all three forms, the order of stability being: slender prismatic + compact --+ hair- like.

It is moderately readily soluble in boiling alcohol, giving a pale yellow solution, from which very slender prisms of the first, or a-form, separate on cooling. These are of such a pale yellow colour that when dry they appear almost colourless. I f the original solution is suficiently concentrated, they grow until the whole liquid is filled with a mass of slender crystals, generally radiatillg from a few points. If these crystals are allowed to, remain in the mother liquor a t the ordinary temperature, small, yellow, six- sided plates of the second, or &modification, soon make their appearance, and raQidly grow at the expense of the first. form, which dissolves in their neighbsurhood, forming cavities OccLIpied by one o r more crystals that, may increase1 t o a considerable size

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898 TRIMORPHIC CHANGE O F 4-NITROACETO-O-TOjiTTT~IDl~.

and are usually well shaped. The traasformatio~l i i i LO tlic secoiitl rorm is generally complete after the lapse of a few days if t h e beaker is left undisturbed, although the time taken depends greatly on the average temperature, and is much shortened by occa$i6nally shaking the transforming mass. When the change is cork;plete, a relatively thin layer of Tvell-Fhaped, compact crystals remains a t the bottom 01 the beaker.

After some time, often before complete transfoi*mation of the first into the second form, a third, or y-modification, makes its appearance in tufts of coloizrless, hair-like crystals resemhlillg :,iiiall colonies of a mould or tiny balls o€ cotton viool. These increase it1 size, the compact form dissolving and disappearing i i i i til ihei whole contents of the beaker become a felted mass liaviiig a superficial resemblance to a somewhat slimy jelly. From this, the niotlier

s liquor is removed oiily with cIiAiculi,y by filtration or pressurr. Direct bransformation of the a- into the y-forin occiirs if the xilaps

o l slender prismatic crystals first separating is seeded with a few crystals of the hair-like form.

All three forms, when heated, soften and melt a t the same temperature, namely, 150-151*, which seems to indicate that before, t h e fusion point is reached transformation into the form most stable near that temperature takes place.

Mr. T. V. Barker, who has very kindly examined the crystals, reports oh them as follows.

The first, or a-modification, crystallises in clotibly refracting needles with straight extinction.

The well-developed crystals of the ,t-modification belong to the mondinic system. Forms : a(100), c(Oo1), n(210), ~ ( o I o ) , ~ ( O I I ) , and ~ ( 1 0 1 ) ; also, occasionally, s(TOl), and, very rarely, ~ ( 0 2 1 ) anci

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’PHE PREPAR.4TION OF ETHYTL~MINE AND OF DIETHYLAMINE. 899

y(Ol2). The general habit and common forms of the crystals are shown in the figure. Crystallographic constante : 57O26‘, n(48°34!)n7 (4l026’)b, 49O43’, 74O10’, or, alternatively, a, : b : c = 1 -178 : 1 : 0-6388, f I = 105O50’. Three crystals were measured on the two-circle goniometer; following are t*he mean values of the most trustlworthy results :

b (010). a (100). n (210). c (001) Azimuth ............ Face of oo 0’ oo 0’ * 7 4 O 10‘ Polar distance ... reference 90 0 “60 28 90 0

Q (011). r (101). Azimuth ............ 74O 10’ 60O113’ (CalC. = 49’ 43’) Polar distance ... “58 265 90 0

Optically, biaxial; axial plane, b(010) ; extinction on b(010), 37’ with prism edge in the obtuse angle f I . Complex-symbol: 4h; + 16/42/ + 38.

The third, o r y-modification, crystallises in hair-like, doubly refracting neetdles with an extinction of 3 5 O .

~JNIVERSITY CHEMIC AT, LARORATORY, d

OXFORD. [I?rc&~rd, October S l s t , 1918. J

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