Times grading

It should be noted that at times grades are used other than as shown here. For instance, chemical (and occasionally polymer) grade can be (and is) used for... 

Times Grading and Scale Dependence of the Phenomena Hierarchy... 

Whereas the couplings are not scale dependent, the times grading can be adjusted since the phenomena involved exhibit various dependencies with respect to the characteristic dimension. Indeed, the characteristic times presented in Table 2.1 are sorted in ascending order of their power dependence on the characteristic geometric dimension. What should be noticed first is the large variation of the scale dependence with respect to the phenomenon. Homogeneous reactions exhibit no dependence on the characteristic dimension whereas transfer phenomena are strongly influenced by the presence of walls and obstacles. 

Purifier Machine used for the removal of bran from middlings while at the same time grading milling stocks into several fractions by size and density. The purifier consists of angle-positioned sieves with different mesh sizes that move longitudinally, and in which controlled air separates fractions with same size but different density. 

The enantiomeric excess of 3.10c has been determined by HPLC analysis using a Daicel Chiracel OD column and eluting with a 60 / 1 (v/v) hexane(HPLC-grade) / 2-propanol(p.a.) mixture. At a flow of 1 ml per minute the rentention times for the different isomers of 3.10c were 6.3 min. (exo, major enantiomer) 7.1 min. (exo, minor enantiomer) 7.7 min. (endo, major enantiomer) 10.7 min. (endo, minor enantiomer). 

The bottoms from the solvent recovery (or a2eotropic dehydration column) are fed to the foremns column where acetic acid, some acryflc acid, and final traces of water are removed overhead. The overhead mixture is sent to an acetic acid purification column where a technical grade of acetic acid suitable for ester manufacture is recovered as a by-product. The bottoms from the acetic acid recovery column are recycled to the reflux to the foremns column. The bottoms from the foremns column are fed to the product column where the glacial acryflc acid of commerce is taken overhead. Bottoms from the product column are stripped to recover acryflc acid values and the high boilers are burned. The principal losses of acryflc acid in this process are to the aqueous raffinate and to the aqueous layer from the dehydration column and to dimeri2ation of acryflc acid to 3-acryloxypropionic acid. If necessary, the product column bottoms stripper may include provision for a short-contact-time cracker to crack this dimer back to acryflc acid (60). 

Thermally activated initiators (qv) such as azobisisobutyroaittile (AIBN), ammonium persulfate, or benzoyl peroxide can be used in solution polymeriza tion, but these initiators (qv) are slow acting at temperatures required for textile-grade polymer processes. Half-hves for this type of initiator are in the range of 10—20 h at 50—60°C (13). Therefore, these initiators are used mainly in batch or semibatch processes where the reaction is carried out over an extended period of time. 

Dissociation of the second proton is insignificant. The pH of its aqueous solutions can be measured reproducibly with a glass electrode, but a correction dependent on the concentration must be added to obtain the tme pH value. Correction values for the most common commercial solutions are Hsted in Table 3. The apparent pH of commercial product solutions can be affected by the type and amount of stabilizers added, and many times the pH is purposely adjusted to a grade specification range. 

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