Sensitivity problem general considerations

In spite of the apparent problems associated with the use of a continuum as an atomic absorption source, some useful absorbance data have been obtained. Sensitivities have generally been considerably poorer than with hollow cathodes by a factor of about ten. 

Four general considerations argue that acid rain is a serious and even urgent problem that needs to be addressed without delay. First, the number of resources threatened by acid rain is large. About one quarter of the smrface water in the eastern U.S. — some 14,000 square miles — is moderately to highly sensitive to acid rain. In Canada, nearly 11,000 square miles of surface water are highly sensitive to acid rain. According to U.S. and Canadian estimates, the number of acidified lakes in eastern North America will double by 1990 at current rates of acid deposition. In addition, nearly 75% of the forest area in the eastern U.S. now receives at least moderately acidic deposition. 

A serious limitation of the STM technique so far is its lack of chemical sensitivity. Generally, STM is not specific for the elemental species in multi-component systems, though there are special cases where the direction of charge flow is well known as shown for the GaAs(llO) surface. The surface area which one is looking at by STM is typically quite small. The problem of how representative the obtained tunnel vision is, is at least partly solved by considerably increasing the total scan range of STM/SPM instruments. 

Two general procedures have been used to obtain AH values. The first involves the measurement of log K values over a range of temperatures the observed variation may be used to derive the required AH value. However, because of the usual errors inherent in log K determinations coupled with the limited temperature range normally possible, AH values obtained in this manner tend to be somewhat unreliable. In contrast, the direct determination of AH using calorimetry commonly results in values which are considerably more accurate. Nevertheless, such calorimetric determinations may still not be easy for particular macrocyclic systems. Difficulties can arise in measuring the total heat evolved for metal complexation when long equilibration times are necessary. To lessen such problems, sensitive calorimeters have been used which are able to integrate the heat released over an extended time. 

Fireworks, when not properly handled, can result in injury, loss of life and property damage. The problems of safety are in many ways different from those of most explosives and propellants. In general, the sensitivity of fireworks to shock and impact is considerably less than that of many explosives and propellants. On the other hand, most fireworks are more sensitive to sparks and flame than most other explosive materials. 

---