General Cautions

Specimen Location Distribution headers, recirculating cooling system 

Environment Internal Cooling water treated with corrosion inhibitors and sodium hypochlorite biocide, 75°F (24°C), 50 psi (345 kPa), pH 7-8 

Sample Specifications 14 in. (35 /2 cm) diameter 316L stainless steel pipe 308L weld filler metal 

Operation of this cooling water system was intermittent, resulting in long periods (30 days) of no-flow conditions. After IVi years, leaks were found at welded pipe junctions. Radiographic examinations revealed numerous additional deep corrosion sites at welds that had not yet begun to leak. 

Several of the welded junctions were removed from the system for metallographic examination (Fig. 15.20). As can be seen from Fig. 15.20, the internal surface was covered with reddish and tan deposits and corrosion products. The metal surface itself retained a bright, metallic luster. 

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In view of the ready commercial availability and apparent stability of the hexahy-drate, it is probable that the earlier report of explosion on impact, and deflagration on rapid heating [1] referred to the material produced by partial dehydration at 100°C, rather than the hexahydrate [2], The caked crystalline hydrated salt, prepared from aqueous perchloric acid and excess cobalt carbonate with subsequent heated evaporation, exploded violently when placed in a mortar and tapped gently to break up the crystalline mass, when a nearby dish of the salt also exploded [3]. Subsequent investigation revealed the probable cause as heating the solid stable hexahydrate to a temperature ( 150°C) at which partial loss of water produced a lower and endothermic hydrate (possibly a trihydrate) capable of explosive decomposition. This hazard may also exist for other hydrated metal perchlorates, and general caution is urged [4,5],... 

The radical scavenging methods require the general caution that the stoichiometry of the reaction between scavenger and radical must be established. A problem with some scavengers is that their reaction with radicals may not be quantitative. The DPPH radical is an extremely efficient scavenger in many systems. It completely stops vinyl acetate and styrene polymerizations even at concentrations below 10 4M [Bartlett and Kwart, 1950]. However, the scavenging effect of DPPH is not universally quantitative for all monomers. 

General caution and safety. The metal alkyls trimethylaluminum, trimethylgallium, trimethylindium, triethylindium, dimethylzinc, and diethyl-zinc all spontaneously inflame in air (pyrophoric) and are violently reactive toward water and carbon dioxide. Dimethylcadmium fumes upon exposure to air but does not inflame, and decomposes, sluggishly, in water. As with cadmium dichloride, and in common with all cadmium compounds, dimethylcadmium is extremely toxic. A dry powder extinguisher, sand bucket, and fire blanket should be at hand at all times. 

Caution. Trimethylindium is pyrophoric. Methyllithium is potentially pyrophoric. The chemicals benzene and methyliodide are highly toxic. See general caution and safety section. 

Caution. Trimethylaluminum is pyrophoric. See general caution and safety section. 

Five-coordinate pentavalent vanadium has never been actually demonstrated for any enzyme, nor is the state of protonation of the bound vanadate known. While monomeric orthovanadate, or one of its protonated forms, appears to be the species responsible for enzyme inhibition, in a few instances the decavanadate may be involved27,28. In general, caution must be exercised when attributing inhibition to a particular species of vanadate. Which vanadate species are present in solution depends markedly on pH and on concentration and, moreover, equilibrium is usually only slowly achieved. 

The use of HRT is generally cautioned in liver disease because of concern over its potential to provoke or worsen cholestasis. This is based on early experience with oral contraceptive pills that contained higher doses of the less degradable synthetic oestrogen ethinylestradiol. However, several studies have demonstrated the safety and efficacy of HRT in patients with chronic liver disease, in particular those with PBC and viral hepatitis. HRT may be particularly beneficial in patients with PBC owing to the high prevalence of osteoporosis in this population. 

Caution. See the recommendations in the general caution above. Procedure... 

Preparation (4, 94). Details for the preparation have been submitted to Organic Synthesis. The phosgenation of amides is general caution the reaction can be exothermic. With less reactive amides DMF can be used as catalyst. AU a-haloenamines are highly hygroscopic. 

Use of diuretics is generally cautioned in persons taking drugs with narrow therapeutic ranges (small differences between the effective and toxic doses), such as warfarin, steroids (i.e., prednisone), digoxin, tacrolimus, cyclosporine, valproic acid, phenytoin, and carbemaze-pine, as shifts in serum levels of sodium and potassium may affect serum levels of these drugs. Serum electrolyte shifts, notably sodium, can also cause an increase in serum... 

The following general cautions should always be observed. 

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