History of solvents

If solvent abuse causes psychological impairment, it follows that not only should the impairment be present in those with a history of solvent abuse, but also that the impairment should not have been present at the same level prior to the beginning of that history. In order to provide a measure of ability antecedent to solvent abuse in the present study, the results of all standardised educational tests that had been administered at or before the time of transfer from primary to secondary school were obtained from the schools. The child s current test performance could therefore be compared with his or her performance prior to solvent abuse, thus making it possible to examine whether the performance of the cases had deteriorated since they started sniffing. These data also made it possible to take account statistically of any differences between groups in ability antecedent to solvent abuse. 

An individually administered self-completed questionnaire was used to ascertain the child s use of solvents during the interval between the initial and follow-up assessments. This was preferred to an interview assessment because, as explained above, the follow-up assessments were not conducted blind , and it was felt that it would be difficult to avoid bias in the degree of thoroughness with which the children were questioned if the examiner was aware of the child s prior history of solvent abuse. The questionnaire was administered at the end of the assessment after all of the psychological tests had been done. It included questions about the use of cigarettes, alcohol and solvents during the interval between the initial and follow-up assessments, and the use of cannabis, amphetamines, cocaine, heroin and any other drugs at any time in the past. 

The statistical significance of the differences between cases and controls on categorical variables was examined by means of chi-squared tests differences between cases and controls on continuous measures were examined using t-tests for matched samples. The effect of frequency of solvent abuse and other multilevel factors relating to history of solvent abuse were examined by means of analyses of variance. Where appropriate, further details of the statistical methods used for particular sets of analyses are provided in the relevant parts of the Results section. 

The main set of variables was used routinely to examine the relationships between psychological test performance and the various aspects of the child s history of solvent abuse the subsidiary set was used only for the basic comparison between cases and controls. 

The cases and controls were compared by subtracting the score of each case from that of its matched control and performing r-tests to examine whether the mean difference scores differed significantly from zero. The effect of frequency of solvent abuse (and other multi-level factors relating to the child s history of solvent abuse) was examined by means of analyses of variance carried out on these mean difference scores to test the hypothesis that the subgroups differed significantly from each other. 

Throughout the history of the development of fats and oils, many wet chemical methods have been developed to assess the quaUty of the raw materials and products. As sophisticated instmmentation develops, many of the wet methods are being replaced. Particular attention is being given to methods that eliminate the use of solvents which cause an environmental disposal problem. Many in-line sensors are also being developed to allow corrections of critical parameters to be made more quickly in the process. 

Most by-product acetylene from ethylene production is hydrogenated to ethylene in the course of separation and purification of ethylene. In this process, however, acetylene can be recovered economically by solvent absorption instead of hydrogenation. Commercial recovery processes based on acetone, dimetbylform amide, or /V-metby1pyrro1idinone have a long history of successfiil operation. The difficulty in using this relatively low cost acetylene is that each 450, 000 t/yr world-scale ethylene plant only produces from 7000 9000 t/yr of acetylene. This is a small volume for an economically scaled derivatives unit. 

Latex Adhesive Applications. Polychloroprene latex adhesives have a long history of use in foil laminating adhesives, facing adhesives, and constmction mastics. Increasingly stringent restrictions on the emission of photoreactive solvents has heightened interest in latex compounds for broader apphcations, particularly contact bond adhesives. Table 10 makes a general comparison of solvent and latex contact bond adhesives (158). 

H. T. Kohlbrand, Case History of a Deflagration Involving an Organic Solvent/Oxygen System Below its Flash Point, Paper presented at AlChE Loss Prevention Symposium, San Diego, Aug. 1990. 

Ionic liquids may be viewed as a new and remarkable class of solvents, or as a type of materials that have a long and useful history. In fact, ionic liquids are both, depending on your point of view. It is absolutely clear though, that whatever ionic liquids are, there has been an explosion of interest in them. Entries in Chemical Abstracts for the term ionic liquids were steady at about twenty per year through 1995, but had grown to over 300 in 2001. The increased interest is clearly due to the realization that these materials, formerly used for specialized electrochemical applications, may have greater utility as reaction solvents. 

The early history of ionic liquid research was dominated by their application as electrochemical solvents. One of the first recognized uses of ionic liquids was as a solvent system for the room-temperature electrodeposition of aluminium [1]. In addition, much of the initial development of ionic liquids was focused on their use as electrolytes for battery and capacitor applications. Electrochemical studies in the ionic liquids have until recently been dominated by work in the room-temperature haloaluminate molten salts. This work has been extensively reviewed [2-9]. Development of non-haloaluminate ionic liquids over the past ten years has resulted in an explosion of research in these systems. However, recent reviews have provided only a cursory look at the application of these new ionic liquids as electrochemical solvents [10, 11]. 

Polylactides, 18 Poly lactones, 18, 43 Poly(L-lactic acid) (PLLA), 22, 41, 42 preparation of, 99-100 Polymer age, 1 Polymer architecture, 6-9 Polymer chains, nonmesogenic units in, 52 Polymer Chemistry (Stevens), 5 Polymeric chiral catalysts, 473-474 Polymeric materials, history of, 1-2 Polymeric MDI (PMDI), 201, 210, 238 Polymerizations. See also Copolymerization Depolymerization Polyesterification Polymers Prepolymerization Repolymerization Ring-opening polymerization Solid-state polymerization Solution polymerization Solvent-free polymerization Step-grown polymerization processes Vapor-phase deposition polymerization acid chloride, 155-157 ADMET, 4, 10, 431-461 anionic, 149, 174, 177-178 batch, 167 bulk, 166, 331 chain-growth, 4 continuous, 167, 548 coupling, 467 Friedel-Crafts, 332-334 Hoechst, 548 hydrolytic, 150-153 influence of water content on, 151-152, 154... 

In a case-control study of pesticide factory workers in Brazil exposed to methyl parathion and formulating solvents, the incidence of chromosomal aberrations in lymphocytes was investigated (De Cassia Stocco et al. 1982). Though dichlorodiphenyltrichloroethane (DDT) was coformulated with methyl parathion, blood DDT levels in the methyl parathion-examined workers and "nonexposed" workers were not significantly different. These workers were presumably exposed to methyl parathion via both inhalation and dermal routes however, a dose level was not reported. The exposed workers showed blood cholinesterase depressions between 50 and 75%. However, the baseline blood cholinesterase levels in nonexposed workers were not reported. No increases in the percentage of lymphocytes with chromosome breaks were found in 15 of these workers who were exposed to methyl parathion from 1 week to up to 7 years as compared with controls. The controls consisted of 13 men who had not been occupationally exposed to any chemical and were of comparable age and socioeconomic level. This study is limited because of concomitant exposure to formulating solvents, the recent history of exposure for the workers was not reported, the selection of the control group was not described adequately, and the sample size was limited. 

This very truncated survey of the history of the study of ligand substitution studies brings us to the present and the question of future directions. Although this review predominantly deals with solvent exchange and monodentate ligand substitution processes, the ideas ex-... 

Sample Preparation. Samples for mechanical studies were made by compression molding the polymers at 150°C between Teflon sheets for 15 minutes followed by rapid quenching to room temperature in air. These will be referred to as PQ (press-quenched or simply quenched) samples. The thickness of the PQ samples was around 10 mils (0.25 mm). The thermal history of all of the PQ samples (HBIB, HIBI, and LDPE) were essentially the same. They were used within one week after they were pressed. Samples for morphology, SALS and SEM studies were prepared from toluene solutions. These films were cast on a Teflon sheet at 80 C from a 1% (by weight) solution in toluene. These films were about 5 mils in thickness. When the polymer films had solidified (after 5 hrs), they were stored in a vacuum oven at 80°C for two days to remove residual solvent. These samples will be designated by TOL (solution cast from toluene). 

Much confusion in the early history of aqueous transition-metal chemistry stemmed from the inability to distinguish free formula ions (serving merely as solvent-separated counterions) from those that remain in direct coordinated contact with... 

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