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This study describes experiments on sediment-estuarine water slurries originating from a Spartina alterniflora salt marsh. We investigated the fate of tin(IV) or monomethyltin cation (MeSn 3+ ) chlorides after their additon to slurries under anaerobic and aerobic conditions. We did not observe methylation of tin in anaerobic or aerobic slurries with and without added tin(IV). MeSn 3+ -amended samples occasionally formed small amounts of Me 2 Sn 2+ or Me 3 Sn + after extended periods of time, particularly when MeSn 3+ remained in solution. The stability of MeSn 3+ in slurries demonstrates that the absence of net methylation of tin(IV) is not due to rapid demethylation of MeSn 3+ or its further methylation. Inorganic tin concentrations in the aqueous phase of anaerobic slurries spiked with MeSn 3+ and unspiked slurries decreased by about 85% in 21 days and remained relatively constant until the end of the 59-day experiments. In similar anaerobic experiments about 25% of the MeSn 3+ spike was adsorbed to sediment within 1 h and about 75% was adsorbed within 10 days. The lack of methylation and demethylation reactions in our aerobic and anaerobic slurries, which contrasts with two previous reports, undoubtedly reflects the absence of added nutrients and low concentrations of added tin(IV) in our experiments. We believe that our model experiments more accurately reflect conditions in salt marshes than do previous studies. We conclude that future model studies on methylation of inorganic tin should include S. alterniflora because it is so prominent in observations of methyltin compounds in the estuary.

A double-blind, placebo controlled, crossover trial of 20 and 40 mg of xipamid once daily in the treatment of mild to moderate hypertension is reported and some of the difficulties and pitfalls of multicentre trials of this type are described. 2 Both doses were significantly more effective in reducing the blood pressure than the placebo and neither was superior to the other. Both produced some potassium loss. Xipamid acted for at least 22 h and was effective in up to 83% of the patients. 3 Further trials are suggested to investigate the activity of a lower dose than 20 mg.

Seven sites in Mississippi, Louisiana and Arkansas have been dated. For six sites (Terral Lewis, Poverty Point, Jaketown, Teoc Creek, Shoe Bayou, and Claiborne) the results are not inconsistent with contemporaneity; excluding Claiborne the average date is 1000 b.c., with an error limit in absolute terms of ± 200 years. The seventh site (Loggy Bayou), in which sherds and balls were found in association, gave a date some fifteen hundred years more recent.

Methyl dodecahedranecarboxylate, C22H22-O2, (4), Mr = 318.42, monoclinic, C2/c, a = 12.600 (2), b = 7.992 (4), c = 28.975 (7) A, beta = 101.79 (2) degrees, V = 2856 A3, Z = 8, Dx = 1.48 g cm-3, lambda(Mo K-alpha) = 0.71073 A, mu = 0.84 cm-1, F(000) = 1360, T = 294 K, R = 0.044 for 2109 unique reflections with Fo2 greater than 3 sigma(Fo2). 21-Phenylcyclopropadodecahedrane, C27H24, (5), Mr = 348.49, tetragonal, P4(2)/n, a = 17.528 (3), c = 10.752 (2) A, V = 3303 A3, Z = 8, Dx = 1.40 g cm-3, lambda(Mo K-alpha) = 0.71069 A, mu = 0.85 cm-1, F(000) = 1488, T = 295 K, R = 0.053 for the 1773 unique reflections with Fo2 greater than 1 sigma(Fo2). The molecular geometries of methoxycarbonyldodecahedrane (4) and 21-phenylcyclopropadodecahedrane (5) are compared to those of the parent C20H20 hydrocarbon (1) and its 1,16-dimethyl derivative (2). For both (2) and (4), the framework is modestly distorted by the substituents, the intracavity distance being more extended along the axis that contains the pendant group(s). Remarkably for (5), its cyclopropane ring has all C-C bonds and internal angles essentially equal, and those dodecahedrane bonds in the immediate vicinity of the ring fusion are extensively perturbed.