Weight loss, measuring

Weight lo.s.s probe.s. Coupons for measuring weight loss are still the primai y type of probe in use. These may be as simple as samples of the process plant materials which have been fitted with electrical connections and readouts to determine intervals for retrieval and weighing, to commercially available coupons of specified material,... 

IX lists the results of some of these experiments, comparing the nitrile materials with polyethylene, the most widely used plastic container material, and poly (vinyl chloride), which is being used for a number of food packaging applications. Note that in all instances there is an order of magnitude difference between the Lopac container and the other two. For flavorants, which are usually present in very low concentrations, this dilute solution test is probably more significant than a standard permeability test which only measures weight losses of the pure ingredient. 

A ketene acetal-terminated prepolymer was first prepared from 2 eq of the diketene acetal 3,9-bis(ethylidene-2,4,8,10-tetraoxaspiro-[5,5]undecane) and 1 eq of the diol 3-raethyl-l,5-pentanediol and. then 30 wt% levonorgestrel, 7 wt% Mg(OH)2j and a 30 mole% excess of 1,2,6-hexanetriol mixed into the prepolymer. This mixture was then extruded into rods and cured. Erosion and drug release from these devices was studied by implanting the rod-shaped devices subcutaneously into rabbits, explanting at various time intervals, and measuring weight loss and residual drug (15). 

Thermal gravitational analysis (TGA) Chemical testing technique that precisely measures weight loss (due to gas forming reactions) as a function of temperature and time. 

Subsequent work on catalyst characterization via reduction studies has involved gravimetric or volumetric techniques. The gravimetric method measures weight loss (due to O loss), while the volumetric method measures amount of H2 consumed [and amount of water formed (O loss)]. In the latter case, the amount of H retained by the catalyst can also be determined (20). The gravimetric technique has also been applied to sulfided catalysts (27). From these measurements, the stoichiometric state of the catalyst can be determined. 

Conventional weight loss measurements in testing inhibitors are time-consuming since measurable weight loss is required to obtain meaningful data on corrosion rates. In general the performance of corrosion inhibitors is expressed in terms of percentage inhibition. 

We already have reported on the replacement of the terephthalic acid with kinked diphenylether dicarboxylic acids (4). 3,4 - and 4,4 -Dicarboxydiphenylether (3,4 -0 and 4,4 -0) were synthesized and all-aromatic polyesters were prepared represented by structure 1. These polyesters were thermotropic with melt transitions decreasing to about 200°C with increasing replacement of the terephthalic acid with the kinked monomers. The polymers generally were thermally stable without measurable weight loss until well over 400°C. We wish here to supplement our previous studies with rheological measurements and fiber spinning of the polymers, including some measurements of fiber properties. 

Since these samples could be fully oven dried and accurately weighed, a comparison between the true balance-measured weight losses and the cumulative experimental stripping rates could be made. For the Bronze 3.0 a 80% chemical recovery was attained, but for the Bronze... 

At temperatures below 150°C, water that is physically attached to clays evaporates. Physically attached water can be present as water adsorbed onto the surface of particles or between the layers of the clay structure. The loss of water is endothermic and results in measurable weight loss. For kaolinite, the weight loss is usually minor, on the order of a percent or less. However, other clays, particularly those that swell when exposed to water such as bentonite can have considerable weight loss in this temperature regime (4-8 wt%) [6], For kaolinite, the changes due to loss of physical water do not alter the structure as determined by X-ray diffraction. 

The principal method for measuring weight loss is thermogravimetric analysis (TGA) [2] ... 

CaCOs was estimated on ashed sediment samples by measuring weight loss after leaching with dilute HCl (e.g., Molnia, 1974). 

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