scholarly journals The estimation of small quantities of carbon dioxide in air by the absorption of infra-red radiation

1940 ◽  
Vol 129 (857) ◽  
pp. 468-474 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Absorption Band ◽  
Water Vapour ◽  
Preliminary Treatment ◽  
Transmitted Radiation ◽  
Infra Red ◽  
Red Radiation

This paper describes an investigation of the possibility of measuring small amounts of carbon dioxide in air by the absorption of infra-red radiation. It is shown that the method is simple, trustworthy and accurate, and is very sensitive for small amounts of carbon dioxide, of the order of that present in ordinary air. The principle is applied in a form superior to any hitherto used, in that the whole of the transmitted radiation is measured instead of merely the radiation at the maximum of a particular absorption band. This makes a spectrometer unnecessary, eliminates the disturbing effect of variation of temperature, and allows much less sensitive detecting apparatus to be used. The only preliminary treatment necessary is the removal of water vapour from the air under examination.

Attraction of Aedes aegypti (L.): responses to human arms, carbon dioxide, and air currents in a new type of olfactometer

1969 ◽  
Vol 58 (3) ◽  
pp. 629-642 ◽  
Author(s):  
M. S. Mayer ◽  
J. D. James
Keyword(s):  
Carbon Dioxide ◽  
Aedes Aegypti ◽  
Large Scale ◽  
Host Location ◽  
Direct Method ◽  
Behavioural Effects ◽  
Infra Red ◽  
New Type ◽  
Red Radiation ◽  
A Current

A new type of olfactometer was designed to study the responses of mosquitos to various stimuli. Hosts could be displayed downwind as well as upwind from the mosquitos, and two hosts could be displayed simultaneously, one upwind from the other. Responses to radiations, if any, and to odours could be measured.Mosquitos were not attracted downwind to an arm displayed within 61 cm., even when they were stimulated by CO2 (under an incident illumination of about 10 foot-candles). About half the mosquitos showed a positive anemotactic response (i.e., they left the end downwind compartment in which they were released) in a current of room air, which undoubtedly contained human emanations. Only 15 per cent, responded to filtered air. Carbon dioxide caused no increase in response to filtered air but increased the number responding to room air (76 per cent, left the end down-wind compartment). Equal numbers of mosquitos responded to an arm displayed upwind in room air and in filtered air, i.e., about 83 per cent, left the end compartment. Carbon dioxide caused no increase in the number of mosquitos responding to an arm but increased the number responding to attenuated emanations from an arm. A repellent (deet) eliminated most of the response to an arm; the addition of carbon dioxide increased upwind flight to the treated arm, but many of the mosquitos flew past it. Carbon dioxide therefore appears to have a synergistic action with arm odours in the attraction of females of Aedes aegypti (L.). However, this conclusion does not exclude other behavioural effects of carbon dioxide demonstrated by other investigators.Eesponses to arms in this new type of olfactometer were nearly identical to those obtained in another type previously used in a large-scale study. The testing confirmed earlier reports that mosquitos do not fly far in the same direction as wind-current and that host location was not possible through positive anemotaxis in the absence of light. Mosquitos were not attracted to a source of infra-red radiation.The new direct method of comparing the attractiveness of different subjects demonstrated that mosquitos would leave the vicinity of one arm and migrate further upwind to another that was more attractive. Water and acetone rinses of human arms reduced attraction; acetone appeared to be a better solvent for the attractant substance than water.

scholarly journals The constitution of water in different states

1934 ◽  
Vol 145 (855) ◽  
pp. 489-508 ◽  
Keyword(s):  
Absorption Band ◽  
Water Vapour ◽  
Relative Intensity ◽  
Liquid State ◽  
Raman Band ◽  
Water Band ◽  
Infra Red ◽  
Triple H ◽  
Increasing Temperature ◽  
Three Components

In a previous communication, the author described the behaviour of water with changes of temperature and with addition of electrolytes as revealed by the changes in the structure of its Raman band. This band is found to consist of three components with mean Raman frequencies 3217, 3433, and 3582 cm. -1 . With increasing temperature, the component 3582 increased in intensity, while the first diminished, the central one remaining nearly constant. A comparison of the above changes with the results obtained by the author for ice indicated that the component which becomes more intense with increasing temperature is absent in the Raman band of ice. The first component with the smallest Raman frequency, however, is very conspicuous in ice, and the central one retains the same relative intensity. The above differences in the structure of the band were explained on the hypothesis that water consists not only of single (H 2 O) but also of double (H 2 O) 2 and triple (H 2 O) 3 molecules, the relative proportions of which depend upon its state of aggregation as well as on its temperature. Ice is supposed to consist only of double and triple molecules, which reveal themselves as the two components of its Raman band. In the liquid state, the presence of all the three components in this band is taken as evidence of the fact that there are all the three types of molecules in this state. No data were then available as regards the Raman band for water-vapour. But the infra-red absorption band observed by Hettner at 2.66 μ has its corresponding component in the water band which is supposed to arise out of the single H 2 O molecules.

Atmospheric transmission in the 1 to 14 μ region

1951 ◽  
Vol 206 (1084) ◽  
pp. 87-107 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Water Vapour ◽  
Strong Dependence ◽  
Wave Length ◽  
Meteorological Conditions ◽  
Spectral Transmission ◽  
Atmospheric Transmission ◽  
Absorption Bands ◽  
Infra Red ◽  
Length Range

The transmission of the atmosphere for radiation of wave-lengths between 1 and 14 μ has been determined at sea-level, and its dependence on meteorological conditions investigated. Measurements have been made over paths of 2264 and 4478 yd., and the correlation with visibility and humidity studied in detail at four chosen wave-lengths, 2.18, 3.61, 10.01 and 11.48 μ ,. Spectral transmission curves for typical conditions have been recorded for the complete range 1 to 14 μ and, in addition to the numerous absorption bands due to water vapour arid carbon dioxide, some bands caused by the rarer constituents, in particular N 2 O and HDO, have been observed. Throughout the wave-length range investigated, the transmission varies with the visibility, the effect being less marked at the longer wave-lengths. For example, when, under typical conditions, the visual transmission falls from 75 to 50% per sea mile, the corresponding change at 2.18 μ is from 85 to 73%, and at 10.01 μ from 87 to 83%. At the latter wave-length there is a strong dependence on the quantity of water vapour in the path. Assuming that the observed variations of infra-red transmission with visibility are due to the scattering of radiation by salt nuclei the characteristics of a suitable size distribution have been calculated. As the humidity increases the nuclei absorb moisture and increase in size. The distribution is in agreement with the limited observations on size and concentration that have been reported. For a visual transmission of 40% per sea mile the radius of the most frequently occurring droplet is calculated to be 0.4 μ .

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