[Studies of structure-determined biological aggressiveness of chrysotile asbestos. I. Model of chrysotile crystalline structure].

Chrysotile is built out of two kinds of layers placed alternately, namely tridymite (silico-oxygenic) and brucite. A tridymite layer is composed of silico-oxygenic tetrahedrons laid planary in the pseudohexagonal order, while magnesium ions coordinated octahedrally in hydroxyl groups produce a brucite layer. Two layers are bound in a chrysotile molecule through substitution of a part of hydroxine groups of the basis of the brucite layer by oxygen ions from the vertex of the tridymite layer tetrahendrons. The size of an elementary chrysotile cell is as follows: a = 5.3A, b = 9.2A, c = 7.3A, beta = 93 Positions (x, y, z) of all atoms in the elementary chrysotile cell were calculated. In calculations hydrogen atoms were neglected because of small atomic dissipation factor (contribution to the structure) and difficulties in their precise location in the elementary cell. The elementary chrysotile cell is composed of two molecules Mg3 [Si2O5] (OH)4. Crystallographic axes of chrysotile structure were directed in relation to the fibre axis. The values of the elementary chrysotile fibre radii are as follows: R = 208A (starting value) and r = 18.2A (minimum value) A theoretic chrysotile pulverulent diffraction pattern was calculated and drawn. The theoretical pulverulent diffraction pattern of chrysotile was compared with chrysotile diffraction pattern in the card JC PDS21-543. A great similarity between the two diffraction patterns was found.