Notes and Problems

The law of definite proportions states that whenever two (or more) elements combine to form a definite compound the ratio by weight of the elements entering that compound is always the same. 

The law of multiple proportions covers the case where two (or more) elements form more than one definite compound. The law of definite proportions applies to each of the compounds, and the law of multiple proportions says that the definite ratios for the separate compounds are to each other in the ratio of small integral numbers. 

Perhaps the most easily visualized statement of the law of multiple proportions is as follows If the same weight of one ele- 

For example, two different substances are known which contain copper and chlorine. In cuprous chloride 63.6 grams of copper are combined with 35.46 grams of chlorine in cupric chloride 63.6 grams of copper are combined with 70.92 grams of chlorine. The weights of chlorine are in the simple integral ratio of 1 2. 

The law of combining weights may be stated as follows For every element a combining weight may be chosen such that in all pure compound substances the ratio of the number of combining weights of the different elements is the ratio of simple integrals. 

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Natta, G Danusso, F. Stereospecific polymerization of styrene. II. Notes and problems of crystalline polystyrene. Chim. Ind. (Milan, Italy) 1958, 40, 445-450 Chem. Abstr. 1958, 52,100986. 

New health-related and environmental applications are included in margin notes and problems. Topics include the health benefits of omega-3 fatty acids, a-hydroxy acids in skin care products, drugs such as Benadryl that contain ammonium salts, chloroethane as a local anesthetic, rebaudioside A (trade name Truvia), a sweetening agent isolated from a plant source, and many others. 

Problems throughout each section and chapter allow students to check whether they have mastered the skills and concepts the particular section is teaching before they move on. Every section in the text works like a mini-tutorial for the students, with key content, supportive art and notes, and problems to allow them to test their understanding. 

The author is much obliged to his colleague. Professor Olev Trass, who was kind enough to make his course notes and problems available. Illustration 1.6, which deals with the analysis of hypothetical concentration profiles, was drawn from this source. 

Applications Research. Specialty chemical producers devote a larger share of their time and costs to appHcations research than do producers of most commodity chemicals. As noted earHer, the most successful specialty chemical producers have been those companies that ate able to respond quickly to customer needs and problems under the conditions found in the customer s plant. This entails having, at the specialty chemical plant, equipment and procedural knowledge which closely approximate those found among customers. Tests can then be mn and a solution to the problem or need may result. If successful, even in part, it can be brought to the customers and tried there. In practice, of course, each customer s plant has some variables which make a single answer or product quite unlikely. Fortunately, slight modifications by the suppHer will often solve the next customer s problem. 

Since the reliability of gas turbines in the power industry has been lower than desired in recent years because of hot-corrosion problems, techniques have been developed to detect and control the parameters that cause these problems. By monitoring the water content and corrosive contaminant in the fuel line, any changes in fuel quality can be noted and corrective measures initiated. The concept here is that Na contaminants in the fuel are caused from external sources such as seawater thus, by monitoring water content, Na content is automatically being monitored. This on-line technique is adequate for lighter distillate fuels. For heavier fuels, a more complete analysis of the fuel should be carried out at least once a month using the batch-type system. The data should be input directly to the computer. The water and corrosion detecting systems also operate in conjunction with the batch analysis for the heavier fuels. 

The various components which make up a shell and tube heat exchanger are shown in Figures 9.63 and 9.64 and these are now considered. Many different mechanical arrangements are used and it is convenient to use a basis tor classification. The standard published by the Tubular Exchanger Manufacturer s Association (TEMA 97 ) is outlined here. It should be added that noting that Saunders 98 has presented a detailed discussion of design codes and problems in fabrication. 

In contrast to (6)-(7), every equation with the number a is solved here on the whole interval tj < t < ij + i- It is interesting to note that in some particular cases solutions of problem (6)-(7) and problem (11)--(12) will coincide. This is certainly true in the situation wdren both / = 0 and La are independent of t. 

Since the initial report of the pH responsive CHEMFET in 1970, CHEMFET s for other species such as Ca , Na", and penicillin have been descril d. In addition, some of these devices have been tested for in vivo or on-line continuous whole blood monitoring. While problems associated with mass production of the more complex CHEMFET s such as those employing enzymes (for example, with the penicillin CHEMFET) have not yet been fully solved, the technology for mass production of the relatively simple pH CHEMFET is api rently now available and problems noted with early devices attributable to irreversible SiO changes and... 

Most displayed decreased blood cholinesterase activity. Many were observed to have affective syndromes (anxiety, fear, aggression), sometimes accompanied by symptoms of depression. Disruption of memory was noted. Vision problems are also caused by long-term contact with OPPs [A64]. In cotton growing regions with intensive OPP use, the number of spontaneous miscarriages and stillbirths was higher than elsewhere [3]. 

Except for problems with delayed or inadequate fixation as noted above, problems with the trichrome stain are usually related to reagents other than the stain. If crystalline material is apparent after the specimen is stained, the crystals are probably mercuric chloride in the fixative which was not adequately removed because the iodine in the alcohol-iodine solution was too weak or because the slide was in this solution too short a time. If crystals are present after treatment with proper-strength iodine-alcohol, they are present in the specimen, which is thus unsatisfactory, and another specimen should be requested. 

We hope that this review of chiral sulfur compounds will be useful to chemists interested in various aspects of chemistry and stereochemistry. The facts and problems discussed provide numerous possibilities for the study of additional stereochemical phenomena at sulfur. As a consequence of the extent of recent research on the application of oiganosulfur compounds in synthesis, further developments in the field of sulfur stereochemistry and especially in the area of asymmetric synthesis may be expected. Looking to the future, it may be said that the static and dynamic stereochemistry of tetra- and pentacoordinate trigonal-bipyramidal sulfur compounds will be and should be the subject of further studies. Similarly, more investigations will be needed to clarify the complex nature of nucleophilic substitution at tri- and tetracoordinate sulfur. Finally, we note that this chapter was intended to be illustrative, not exhaustive therefore, we apologize to the authors whose important work could not be included. 

Sometimes surprises occur due to unforeseen factors, but sometimes surprises result from gaps in communication. The process analytical chemist should seek the input of process chemists, engineers, and operators early in the project to maximize the chances of learning about relevant known problems. They should spend time at the plant talking to people very familiar with the process. They should ask a lot of questions, and note and pursue any inconsistencies or gaps in the answers. 

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