Hexamethylene tetramine crystals

The Stokes method is essentially a Fourier transform method making use of the entire profile, and is a reasonably straightforward computation, although limits have to be applied to the profile in transform space to achieve correct results. The main peak from hexamethylene tetramine crystals compacted at 85°C (17) has been used as our standard for the instrumental broadening peak. 

Figure 5-2 Comparison of the growth rate of hexamethylene tetramine crystals as a function of super-saturation in aqueous solution and in ethanol solution. (Reproduced with permission from Davey et al. 1982.)...

Formic Aldehyde.—This aldehjde, H. CHO, is the lowest member of the aliphatic series. It has been found, but rarely, in the distUlation waters of a few essential oils. It can be identified by evaporation on a watsr-bath with ammonia when crystals of hexamethylene-tetramine are formed. 

An additive compound is also formed with hexamethylene tetramine this consists of crystals melting at 122° C. (Nef). 

A third possibility is to fiirther crystallize the mother liquor yielding a more impure APT [5.55], Also, treatment of mother liquor with hexamethylene tetramine to precipitate tungsten was proposed [5.56]. 

With anisodimensional molecules states have indeed been observed which lie between the crystalline and the amorphous (mesophases, liquid crystals). Mark recognizes the following transitions between solid crystals and amorphous liquids 1°. Three-dimensional crystal the centres of gravity of the units are fixed (apart from vibration), rotations are not possible. Examples hexamethylene tetramine, urea. 2°, Crystal with rotating molecules the centres of the particles are fixed rotation about one or more axes is possible. Examples NH4CI, sodium stearate at higher temperatures. 

In many cases crystal form and crystal habit may be represented very clearly by space models. Although we may not be able to make such exact assertions regarding crystal structure in a given molecule as in ionic lattices, a number of qualitative relationships can be adduced. Groth, in his chemical crystallography, formulated a relation between molecular structure and crystal structure for molecular lattices and Duden and Scharff many years ago inferred from the cubic crystal structure of hexamethylene tetramine a high symmetry of the molecule which was later confirmed by x-ray analysis. 

Other starting materials that produce hexamethylene tetramine in situ such as formaldehyde with aqueous ammonia or formaldehyde with an ammonium salt (e.g., sulfate) can be used instead of hexamethylenetetramine [68, 122]. The yield of HMTD is, however, low for the latter mentioned example (Matyas and Pachman Unpublished). Ethanol (in large excess about 1 1 per 1 g HMTD) is recommended for purification of HMTD by crystallization [112]. 

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