Warm leads

Waterfeld, A. et al., Angew. Chem. (Intern. Ed.), 1981, 20, 1017 In the preparation of chloriminosulfur tetrafluoride or its dimer by slowly warming a mixture at -196° to -78°C and then ambient temperature, too rapid warming leads to violent explosions. 

The reagent as supplied by manufacturers is moistened with glacial acetic acid to prevent hydrolytic decomposition. It may be prepared in the laboratory by warming lead oxide (red lead, Pb304) with acetic acid in the presence of sufficient acetic anhydride to combine with the water formed. 

The hydrolysis of (99) to diazoalkane (100) is a little tricky, since the methyl ester is also subject to saponification. It was found that addition of 4 equiv. of methanol to the 50% KOH/ether mixture, stirred rapidly in an ice-water bath, followed by addition of (99), gave optimal yields (30-40%) of (100). The reaction mixture must be kept at ice temperature, as warming leads to emulsification and yield loss. 

In fact, a negative feedback exists. Reduction of carbonate to organic carbon leaves the divalent cations Mg " " or Ca " " in its wake. An excess of these cations speeds carbonate burial. [The Urey cycle of stabilizing climate is based on this effect (see Ref. [46] for review). Weathering releases more divalent cations when the climate is warm leading to an enhanced CO2 sink.] A dearth of divalent cations retards the burial of carbonate. 

Commonly in chemistry, we do not teach about feedback cycles in this way, but they can be a helpful way to think about an abstract explanation with older students. The feedback cycle offers a useful tool for thinking about systems that link across the sciences. Homeostasis in the body depends upon such cycles. In physics there are a number of phenomena that can be described with the same very simple feedback structure as in Figure 3.1 (cooling of a hot object, radioactive decay, capacitor discharge, for example). Feedback cycles are also very useful in thinking about aspects of Earth and environmental sciences (for example the possibility of a positive feedback cycle when atmospheric warming leads to warmer seas in which the greenhouse gas carbon dioxide is less soluble). 

An iodo-laurionite Pb(OH)I is made from a solution of lead acetate and warm lead iodide solution. 

And not only are you generating more leads, but you re generating better leads. By better leads, 1 mean warmer leads. What are warm leads They are potential customers who are very close to purchasing by the time they reach your sales teams — which means happier sales executives, happier marketers, and more customers. 

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