In the conventional Verneuil growth of ruby, it is shown that certain parameters pertinent to the final concentration of the additive in the crystal product (solid solution) are: starting concentration, surface distribution of additive in the powder, trajection distance, and growth rate. The effects of these factors are studied at the trajection (or melting) zone.

1.
R. C.
Pastor
,
H.
Kimura
,
L.
Podoksik
, and
M. A.
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J. Chem. Phys.
43
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(
1965
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2.
See W. H. Bauer and W. G. Field in The Art and Science of Growing Crystals, J. J. Gilman, Ed. (John Wiley & Sons, Inc., New York, 1963), Chap. 20 and references cited.
See also S. K. Popov’s article in Growth of Crystals, A. V. Shubnikov and N. N. Sheftal, Eds. (Consultants Bureau Enterprises, Inc., New York, 1959), Vol. 2, p. 103 of translation.
3.
Temperature is used not in the sense of a thermodynamic coordinate but as a steady‐state parameter.
4.
We have employed the loaded free flame to assess contamination from the muffle. Ruby grown without a muffle, e.g., alundum, shows a lower content of Mg (⁠<1 vs 2 ppm) and Ca (2 vs 9 ppm).
5.
Some of these features are seen in the work of
G. A.
Mukhin
,
N. I.
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6.
Powder velocity is close to that of carrier gas. In a typical operation, the carrier flow is ̃6×103 cm3 min−1 through a 0.3‐cm orifice (muzzle velocity ̃14 m sec−1⁠). The orifice feeds into a muffle diameter ̃3.6 cm which reduces carrier‐gas velocity to ̃0.1 m sec−1. Viscous damping slows particles down. Along the axis, however, particles move at higher speeds.
7.
See E. Ryshkewitch, Oxide Ceramics (Academic Press Inc., New York, 1960), p. 118.
8.
E. Ryshkewitch, Ref. 7, pp. 128–129.
9.
The upper limit is set by the more subtle features which characterize boule quality and which have a higher‐order dependence on heat balance.
10.
G. W.
Dueker
,
C. M.
Kellington
,
M.
Katzmann
, and
J. G.
Atwood
,
Appl. Opt.
4
,
109
(
1965
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11.
This may be a combined effect of a decreased powder flow and a surge in fuel flow.
12.
See Ref. 1. Since the powder employed in the present case is also 0.075 at. % Cr, this would mean that 0.030 at. % was in the form of Cr (VI).
13.
This is a different steady‐state setting from that used in the determinations of Fig. 4.
14.
The results of transformation are given in the Ref. 1.
15.
This is not true in the growth zone where the residence time is three orders of magnitude longer. Redox processes are possible in this region, e.g., Al2O3:Mn4+. Such a study has been made in ruby. See
R. H.
Hoskins
 and
B. H.
Soffer
,
Phys. Rev.
133
,
A490
(
1964
).
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© 1966 American Institute of Physics.
1966
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