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Isotopic vapor-pressure differences between (CH3)2CO and (CD3)2CO have been measured by differential capacitance manometry. When combined with available absolute vapor pressures for (CH3)2CO the results may be expressed (206 to 333 K) as: 1n ( p H p D ) = 3642.6(K/T) 2 − 22.205(K/T) + 0.01129

Solvent vapor pressure isotope effects have been measured in HOH/DOD between approximately 0 and 90°C on the following electrolyte solutions: NaBr (2, 5, 7, and 9m), NaI (4, 6, 8, and 10m), KF (3, 6, 9, and 12m), Na2SO4 (2m and saturated solutions, and hydrated cyrstal), and CaCl2 (3, 5.5, 8, and 10m, and hydrated crystal). Values of the isotope effects on the various excess thermodynamic properties of solution, including the osmotic and activity coefficients and the excess free energies, enthalpies, and entropies, have been extracted from least-square expressions which fit the VPIE over the entire concentration and temperature range. The results are compared with those obtained for alkali metal chloride solutions (I, II) and literature data where possible. They are discussed briefly in terms of solution structure.

The transovarial development of Rickettsia tsutsugamushi in a colony of Leptotrombidium (Leptotrombidium) akamushi , a mite vector of scrub typhus, has been studied over 5 generations. The transovarial infection rate was 98%; the filial infection rate was usually 100%, though lower rates were occasionally observed. These rates may not be valid for all populations of vector mites because they have been estimated for female mites producing only female offspring. Nevertheless, these studies show that transovarial passage of rickettsiae can be highly efficient. By this mechanism, point foci of virtually 100% infected larval mites could be produced. The risk of infection for man exposed to larval mites in such point loci would be extremely high.

Leptotrombidium (L.) arenicola, described by Traub in 1960, has previously been shown to harbor Rickettsia tsutsugamushi , the causative agent of scrub typhus. In an attempt to establish the epidemiological importance of L. (L.) arenicola in the transmission of scrub typhus, studies of the behavior of R. tsutsugamushi in this vector were instituted. Transovarial transmission of R. tsutsugamushi through 2 generations of this trombiculid mite was demonstrated. In addition, these experiments showed that L. (L.) arenicola larvae can transmit scrub typhus rickettsiae during feeding on a mammalian host. Because L. (L.) arenicola is widely distributed along the sandy shorelines of both the eastern and western sides of the Malay peninsula. it is concluded that this vector may have considerable epidemiological importance in the transmission of scrub typhus.