Chlorine content, measurement

In solutions, the concentration of available chlorine in the form of hypochlorite or hypochlorous acid is called free-available chlorine. The available chlorine in the form of undissociated A/-chloro compounds is called combined-available chlorine. Several analytical methods can be used to distinguish between free- and combined-available chlorine (8). Bleaches that do not form hypochlorite in solution like chlorine dioxide and nonchlorine bleaches can be characterized by thek equivalent available chlorine content. This can be calculated from equation 5 by substituting the number of electrons accepted divided by two for the number of active chlorine atoms. It can also be measured by iodomettic titration. 

The side-chain chlorine contents of benzyl chloride, benzal chloride, and benzotrichlorides are determined by hydrolysis with methanolic sodium hydroxide followed by titration with silver nitrate. Total chlorine determination, including ring chlorine, is made by standard combustion methods (55). Several procedures for the gas chromatographic analysis of chlorotoluene mixtures have been described (56,57). Proton and nuclear magnetic resonance shifts, characteristic iafrared absorption bands, and principal mass spectral peaks have been summarized including sources of reference spectra (58). Procedures for measuring trace benzyl chloride ia air (59) and ia water (60) have been described. 

It is also shown that organic-chlorine residues on alfalfa hay resulting from insecticide applications of toxaphene and the organic-chlorine content of beef fat from animals fed alfalfa hay containing toxaphene residues or sprayed with benzene hexachloride or DDT approximate a true measure of the amounts of these compounds present. 

Plotting the oxygen content measured at a current density of 4 kA m-2 versus the measured anolyte pH, the relationship as shown in Fig. 16.11 is obtained as expected. This proves again the high internal anolyte circulation of the KU Single Element that makes possible an oxygen content of 0.6% in chlorine at an anolyte pH of only 2.5. 

Possible environmental applications of NIR probes include the measurement of trace amounts of metal pollutants in surface and ground waters and water saturated soils and sediments and the detection of lead, chromium, and other heavy metal ions for efforts in pollution control. Also OFCD could assist in the determination of caustic soda and chlorine contents in wastewaters. 

Long-range effects of having less ozone in the stratosphere involve greater ultraviolet sunlight transmission, alteration of weather, and an increased risk of skin cancer. The ozone depletion potential for CFCs and other fluorocarbons have been measured and are given below relative to CFC-11 and -12. Notice that the HCFCs with lower chlorine content have lower depletion potentials than the CFCs, and the one HFC studied shows no depletion potential because it contains no chlorine. 

The compound is digested with nitric acid and the solution is analyzed for antimony by AA or ICP spectrophotometry (see Antimony). To determine the chlorine content a measured amount of substance is heated at 300°C and the liberated CI2 is passed into an acidic solution of KI and analyzed by iodomet-ric titration using a standard solution of sodium thiosulfate or phenyl arsine oxide and starch indicator. 

Measuring Methods. Chlorine content was determined by the oxygen flask method (2) on a polymer purified by precipitation from the solution in cyclohexanone. Thermal stability, as HC1 evolution, was determined according to ASTM method D-793-49, determining the quantity of HC1 evolved by the polymer maintained at 180 °C in a nitrogen atmosphere. From the slope of the straight line for the amount of HC1 evolved with time, the constant K for the dehydrochlorination rate (DHC) is deduced. 

Figure 15 gives the same measurements for samples A7, B7, and A10 (Table V) of CPVC all obtained by swollen processes. The higher the chlorine content, the higher the temperature of the transition from brittle to tough behavior, and the higher the chlorine content, the lower the value of the impact strength lzod, beyond the transition zone. 

Because of evidence that BCME is carcinogenic even at very low levels in the atmosphere, current studies of its analysis are concentrating on extending the detection limit to even lower levels. Because of its chlorine content, BCME can be measured with extreme sensitivity by electron capture detection after gas chromatographic separation of this analyte. Efforts are underway by Dr. Robert Sievers (University of Colorado, Boulder) to improve collection methods that meet the criteria of (1) highly efficient collection of BCME at sub-ppb levels in air, (2) no loss of analyte from hydrolysis resulting from atmospheric humidity, and (3) rapid, efficient, nondestructive desorption of analyte from the collection medium. 

As mentioned earlier, the starting materials are of high purity. Because we work in a closed system and because we have an electrodeless discharge there should be no sources of additional impurities. Neutron activation analysis revealed that all the transition metal impurities that strongly affect the transmission properties of the optical fibers are lower than 1 ppm. From fiber transmission measurements we know that, besides traces of OH, some impurities must be lower than 1 ppb because only the intrinsic attenuation of the material is found. The chlorine content is rather large at 0.1%, even at the deposition temperature of 1000 °C. Fortunately the chlorine does not affect the optical properties in the interesting region of 0.6 pm - 1.5 pm. 

Substantial amounts of chloride are present in the fixed ruthenium oxide-based films, e.g. about 4% for a preparation temperature of 400°C [194, 195]. The chlorine content has been observed to decrease slightly on going to the external surface as indicated by, for example, secondary ion mass spectrometry [196]. The exact location of chlorine in the bulk lattice is somewhat unclear at present. Oxygen content has been found to increase sharply over the last few monolayers at the external surface, as shown by SIMS [196] and XPS measurements for powders [197] and films [198], There is now evidence from several groups that suggests the existence of some Ru03 in the surface regions of ruthenium dioxide electrodes [196-200]. 

Characterization of the Platinum Functions. It was reported that the hydrogen adsorption represented as H/Pt measured by Hj-Oj titration at 90°C was proportional to the dehydrogenation activity of a catalyst (7), even when the chlorine content varied greatly. Therefore the catalytic platinum functions was characterized by this... 

Although the catalysts showed high initial activity, rapid deactivation was also observed. For example, when using a Pt/t -alumina catalyst at 250 C, essentially complete TCA conversion was observed initially however, after 15 h TCA conversion had declined to < 25 percent. To understand the deactivation process, surface acidity and basicity, coke content, chlorine content, and platinum content were measured for both the fresh and the used catalysts. These measurements showed that up to 40 wt% coke formed on the supported platinum catalyst and that the acidity changed significantly during the reaction at 350°C. 

Platinum and chlorine content also changed. There appeared to be a 14 percent loss in Pt after 96 h, although there was no significant trend with respect to distance. Loss in Pt was unexpected and there is no clear reason for it at this time. Repeat ICP-MS analysis of the fresh catalyst showed <1 percent variability, suggesting that this difference is significant and not due to reproducibility problems. The difference may be due to inaccuracy in the coke measurement, since the measured Pt concentration was corrected to a fresh catalyst . Chlorine content appeared to increase with reactor distance. However, the measured chlorine content only included what was water extractable, and not what might be chemisorbed to the Pt, reacted with the alumina, or part of the coke. 

Supports and Catalysts. The catalyst supports used in this work are described in Table I. The surface areas, except for the sillcalite, were measured by the multi-point BET method. The surface area for the sillcalite was obtained from the manufacturer. Silicalite is an essentially aluminum-free pentasil zeolite (14) manufactured by Union Carbide. The chlorine contents of the supports were determined by neutron activation analysis, and sulfur contents were obtained with a Leco sulfur analyser. Sulfur and chlorine contents were measured since these elements may influence subsequent hydrogen adsorption on the supported platinum catalysts (15). 

Elementary analysis measurements were carried out on an automatic CHN-analyser (Perkin-Elmer 2400, USA). The chlorine content was determined by AgNOj titration. The exact amount of carbon and chlorine residues in the catalysts was determined from three independent measurements. 

The CPE material used in this study is CM 0342 supplied by The Dow Chemical Ccxnpany. This CPE grade has a specific gravity of 1.25, a chlorine content of 42 percent, an average Mooney Viscosity [HLl-i-4 (lOO C) ] of 65 eind a residual crystallinity of less than 2 percent. Molded slabs of the pure and compounded polymer were used. Molding was conducted at 163 C for ten minutes which for most compounds is an optimum cure condition. Samples molded under other conditions will be so noted in the text. For dehydrochlorination measurements the samples were cut into ediout 2 mm cubes. 

Dermal absorption of PCBs has been measured in monkeys and guinea pigs by comparing excretion following topical administration to excretion following parenteral administration. Single doses of " C-labeled PCBs (42% chlorine content) in benzene/hexane were applied to the abdominal skin of four... 

In the case of PVC/PHMA system, the graded structures of the samples could not be examined by FTIR-ATR and DSC methods, because PHMA was very soft at r.t. and that DSC curve did not indicate clear change around Tg. Thus, the graded structure was measured by SEM-EDX method(Fig. 5). The chlorine content in the sample increased gradually towards the petri glass side, and then it is considered to have wide graded structure. 

Before activity measurements, the different catalysts were either dechlorinated at 500°C for 10 h in a stream of N2 + 10 % H2O or thermally aged at 900°C for 16 h in a stream of 1 % O2, 10 % H2O, 10 % CO2, N2, and then reduced at 500°C. The dechlorination treatment was carried out in order to avoid the inhibiting effect of chlorine on the activity of metals for oxidation reactions (2). The chlorine content of dechlorinated samples was below 0.2 wt %. Metal and lanthanum oxide loadings of the various catalysts are reported in Table 1. 

---