Moisture specification

Fumaric acid is sold as resia-grade and food-grade. The general sales specification under which resia-grade fumaric acid is sold ia the United States specifies white, crystalline granules with a minimum assay of 99.6% and maximum ash content of 0.05%. The moisture specification is 0.3% maximum with < 10 ppm heavy metals. The color of a 5% solution ia methanol is to be less than 10 APHA. Food-grade fumaric acid calls for somewhat lower impurity levels. Particle size and particle size distribution are important ia many appHcations. 

The control system requires the values of T and AT obsei-ved during the first minutes of operation to be stored as the basis for the above calculation of end point. When the exhaust temperature then reaches the value calculated, diying is terminated. Coefficient K can be estimated from models but requires adjustment on-hne to reach product specifications repeatedly. Products having different moisture specifications or particle size will require different settings of K, but the system does compensate for variations in feed moisture, batch size, air moisture, and inlet temperature. Some exhaust air may be recirculated to control the dewpoint of the inlet air, thereby consei-v-ing energy toward the end of the batch and when the ambient air is especially diy. 

Report of the Advisory Panel on Moisture Specifications (Chair G. Zografi), Pharmacopeial Forum, 17, 1459 (1991). 

There is little that can be done to affect the chemical composition of the ash as far as SiO A1203, and Fe203 are concerned. The chemical composition of the post-combustion ash is primarily a function of the chemical composition of the non-combustible matter in the coal feed to the boiler. The moisture specification is primarily for storage and handling considerations since fly ash used as a pozzolan has historically been stored, transported, and metered as a dry product. There is no technical reason that fly ash must be dry for use as a concrete admixture. 

Several adjustments were made to the formula and process to improve the com-pactibility of this product. The moisture specification was adjusted, additional dry binder was added to the formula, and the tooling design was re-engineered. 

The defined range suitable for acceptable stability may approach the variability of the moisture determination method or may be as great as a few percent. For example, many lyophilized products with the USP have a finished product residual moisture specification of less than 2% of dry weight. Other products, such as amphotericin B, have a residual moisture limit of 8.0% [31]. Whether the allowable residual moisture specification is small or large, a range of acceptable residual moisture needs to be identified and correlated to suitable long-term stability. 

A USP Advisory Panel on Moisture Specifications initiated a revision process with the inclusion of background material in the general chapter (1241) Water-Solid Interactions in Pharmaceutical Systems. However, this occurred over 10 years ago and it has not been followed by the inclusion of standard analytical tests that can be used to characterize the state of water. 

Although the conformity index should provide a measurement of the total quality of the product, including the adherence to moisture specifications, Plugge and van der Vlies also developed a quantitative calibration for water. With Karl Fischer as reference, their calibration covered the range from 7.1 to 11.6% moisture and used 1642 and 1930 nm to give suitable linearity. 

Natural gas transported through common carrier pipelines must meet a moisture specification of 7 Ib/MMscf of water. Gas is usually dried to meet this requirement by scrubbing with a concentrated glycol solution. Figure 24—1 shows a standard glycol contactor tower, generator, and pump. 

After fixing the leak, this reboiler and the units that had suffered from an inefficient pump and a faulty temperature controller were put back online. The treated natural gas was checked and found to meet pipeline moisture specifications. 

The ability to use atmospheric moisture is a striking feature of the lichen s water relations. Except for some epiphytes, higher plants are inferior to lichens in this respect. But, according to new data (Breazeale et al., 1951 Slatyer, 1956 Hiibner, 1960, Samuilov, 1963), the ability to absorb atmospheric moisture, specifically during night hours with the increased atmospheric humidity may not be unimportant for the water relations of higher plants. 

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