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A study by Franklin, Kraus and their co-workers of many different reactions' in liquid ammonia as solvent has served to establish definitely the existence of a series of ammond-compounds which are derived from ammonia, as the parent substance, in much the same way that the usual acids, bases and salts are related to water. Other investigators have shown that this behavior is by no means limited only to water and ammonia as solvents. Many other substances, such as hydrazine, hydrogen sulphide, hydroxylamine, acetic acid, phosgene and sulphur dioxide may serve as parent solvents for solvo-systems2 of acids, bases and salts. General recognition of these facts has resulted in a decided change in opinion as to the definitions of certain classes of compounds, particularly when it was shown that many so-called salts, when dissolved in solvents other than water, exhibited properties typical of acids. Further than this, the acid or basic character of many substances, as defined by their behavior in water, was found to change completely upon solution in other solvents. Thus, urea reacts with the ammono-base, sodium amide, in liquid ammonia to yield a well-defined salt, but in 100 per cent acetic acid it may be titrated with perchloric acid. Such apparent anomalies made it necessary to characterize an acid or a base specifically in relation to a particular solvent. Considerable confusion resulted, especially with respect to nomenclature, since the number of solvent systems could apparently be increased without limit.

Halogens as transport agentsWO 2 I(s) + 1 2 I 2 (g) # WO 2 I 2 (g) Halides as transport agentsTe 6 O 11 Cl 2 (s) + 5 TeCl 4 (g) # 11 TeOCl 2 (g) Water as transport agentThe CVT of chalcogenide halides is probably described less detailed than the transports of the corresponding binary chalcogenides and halides, respectively. If there are sufficiently stable solid compounds MQ y X z in a system MQ q .MX x , the knowledge of the gas-phase composition over this solid is important for the understanding of the transport characteristics of the total system. Especially during transport reactions of binary oxides, sulfides, selenides, and tellurides, the co-existing chalcogenide halides can condense by adding larger amounts of halogens or halogen compounds as trans-

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