Acid stage

Polymerization of the dianhydride and diamine proceeds through an intermediate poly(amide acid) stage before ring closure converts the adjacent acid and amide groups to the polyetherimide (94). The polymerization can be carried directiy to the polyetherimide as a single-step process, or first to an ainide—acid-containing prepolymer, which can be isolated, and then to the polyetherimide. 

However, the removal of the angular substituent can be made a very efficient process by first oxidizing the 19-hydroxyl to the aldehyde or acid stage. This procedure, first described by Haglwara" has since been applied to a large variety of 19-hydroxy steroids. 

Special precautions must be taken so that the reaction does not stop at the p-toluic acid stage. One approach is to esterify toluic acid as it is formed with methanol. This facilitates the oxidation of the second methyl group. The resulting dimethyl terephthalate (DMT) may be hydrolyzed to terephthalic acid. 

Figure 6 Comparison of actual and model skin curves during wormholing of 15 / HC1 (first acid stage of Well B treatment).

Again, according to Equations 6 and 13, the theoretical response during the acid stage, if wormholing were to take place, would be ... 

Severe hypochromic microcytic anemia, responding only to vitamin B6 and not to iron, a typical symptom of B6 deficiency in many species of animals, is related to the dependence of porphyrin biosynthesis on vitamin Be, preceding the 8-aminolevulinic acid stage, at the condensation of glycine with succinate to yield a-amino- 3-ketoadipate, the immediate precursor of 8-aminolevulinic acid. 

Sierka, R.A. Cooper, S.P. Pagoria, P.S. Ultrafiltration and reverse osmosis treatment of an acid stage wastewater. Water Sci. Technol. 1997, 35 (2-5), 155-161. 

The fact that purine degradation in humans already stops at the uric acid stage can lead to problems, since—in contrast to allantoin—uric acid is poorly soluble in water. When large amounts of uric acid are formed or uric acid processing is disturbed, excessive concentrations of uric acid can develop in the blood hyperuricemia). This can result in the accumulation of uric acid crystals in the body. Deposition of these crystals in the joints can cause very painful attacks of gout. 

These hypolipidemic agents are noncompetitive inhibitors of the enzyme that limit the rate of cholesterol synthesis in the liver at the levalonic acid stage. 

Although many workers have been interested in the production of oxalic acid from sucrose, it is probably true that sucrose cannot compete with other raw materials as a source of this acid. For example, sawdust has been found to be an excellent source of oxalic acid. It is possible, however, to arrest the oxidation of sucrose before the oxalic acid stage is reached and the much more valuable tartaric acid has been obtained in this way. Tartaric acid, at the moment manufactured from waste... 

If toluene is chlorinated to benzo-trichloride, the substitution reaction has oxidized the carbon atom of the methyl group to the acid stage and no further oxidation is necessary. At that point, hydrolysis alone is sufficient ... 

An advantage possessed by this series of changes is that it explains more satisfactorily than the preceding theory why much sulphuric acid can be formed in the Glover tower. In the lead chambers the acid formed is so weak that the nitrososulphonic acid stage is possibly absent from the series. 

The concentration of the acid recycled to the digestion process depends on the quality of the titanium-containing raw material. For raw materials with a high titanium content, the 65-70% sulfuric acid separated from the metal sulfates must be further concentrated to give 80-87% acid (stage 5). 

Delayed release product In appli-cation/compendial release requirements plus dissolution tests in 0.1 N HC1 for 2 hr (acid stage) followed by testing in USP buffer media (pH 4.5-7.5) under application/compendia test conditions and two additional agitation speeds. Application/compen-dial method may be either apparatus 1 or apparatus 2.1 Adequate sampling should be performed (15, 30, 45, 60, and 120 min until either 80% of drug is released or asymptote is reached). Testing should be performed on changed product and biobatch or marketed product. 

Delayed release product In application/compendial release requirements plus dissolution tests in 0.1 N HC1 for 2 hr (acid stage)... 

Figure 3. Expansion characteristics of model acrylic latexes as determined by sedimentation ((%) 2% acrylic acid—Stage II no acid)...

Figure 6. Expansion characteristics of PMMA latexes containing 2% ((%), d0 = 0.10 pm) and 3% (YH)> = 0.11 pm) acrylic acid (Stage II) as determined by...

---