Problem 4 Sodium Effect

However, the disposal of spent groundwood bleach liquor from zinc hydrosulfite has posed zinc toxicity problems for shellfish, so that mills have now switched to sodium hydrosulfite. This is equally effective (although more expensive) and avoids this problem. Sodium hydrosulfite is made at the mill from purchased sodium borohydride (Eq. 15.42). 

Precipitation of sodium paraperiodate (potassium salt not a problem) synergistic effects ... 

There are several things that can be done to combat this problem. Most effective is to avoid purchase of fuel oils with high sodium contents. While vanadium in fuel oil cannot normally be controlled by the refiner (i.e., crude oil will contain an intrinsic amount of vanadium), the sodium content of fuel can be minimized by the refinery producing the residual oil. 

Water-soluble contrast media (CM) are preferred because of effective mixing with CSF, plus the radiopaque is absorbed and effectively excreted in the urine, and does not have to be physically removed from the subarachnoid space after the procedure. Sodium methiodal, the first water-soluble agent used for myelography, produced neurotoxicity problems when exposed to the cells of the spinal cord and brain, thus limiting utility to the lumbar region and requiring the appHcation of spinal or general anesthesia. 

Tendering Effects. CeUulosic materials dyed with sulfur black have been known to suffer degradation by acid tendering when stored under moist warm conditions. This effect may result from the Hberation of small quantities of sulfuric acid which occurs when some of the polysulfide links of the sulfur dye are mptured. A buffer, such as sodium acetate, or a dilute alkaH in the final rinse, especially after oxidation in acidic conditions, may prevent this occurrence. Copper salts should never be used with sulfur black dyes because they cataly2e sulfuric acid generation. Few instances of tendering with sulfur dyes other than black occur and the problem is largely confined to cotton. 

The efforts of the detergent industry toward solution of its part of the eutrophication problem are, at this point, less complete than its response to the biodegradabihty problem. Soda ash, Na2C02, sodium siUcate, and, to a lesser extent, sodium citrate formed the basis of the early formulations marketed in the areas where phosphates were harmed. Technically, these substances are considerably less effective than sodium tripolyphosphate. As a precipitant builder, soda ash can lead to undesirable deposits of calcium carbonate on textiles and on washing machines. 

For example, chloride and duoride ions, even in trace amounts (ppm), could cause the dissolution of aluminum metallization of complimentary metal oxide semiconductor (CMOS) devices. CMOS is likely to be the trend of VLSI technology and sodium chloride is a common contaminant. The protection of these devices from the effects of these mobile ions is an absolute requirement. The use of an ultrahigh purity encapsulant to encapsulate the passivated IC is the answer to some mobile ion contaminant problems. 

It is interesting to note that although the first examples of template effects were observed in nitrogen macrocycles (see chapter 2) no template effect appears to operate in the synthesis of 72. Richman and Atkins note this in their original report . The authors replaced the sodium cation with tetramethylammonium cations and still obtained greater than 50% yield of tetra-N-tosyl-72. Shaw considered this problem and suggested that because of the bulky N-tosyl groups, .. . the loss of internal entropy on cyclization is small He offered this as an explanation for the apparent lack of a template effect in the cyclization. 

The water phase of oil-base mud can be freshwater, or various solutions of calcium chloride (CaCl ) or sodium chloride (NaCl). The concentration and composition of the water phase in oil-base mud determines its ability to solve the hydratable shale problem. Oil-base muds containing freshwater are very effective in most water-sensitive shales. The external phase of oil-base mud is oil and does not allow the water to contact the formation the shales are thereby prevented from becoming water wet and dispersing into the mud or caving into the hole. 

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