Tris fractionation

The interval between the third and fourth appeared in some degree to correspond to what had been expected. That between the fourth and fifth was doubtful, from the loss of the latter, and from ita apparently containing an admixture of unchanged cotton but On trying fractional additions of water, a corresponding intermediate increase of weight was likewise produced in the ootton for example,... 

Kruger [113] tried fractionating nitrocellulose by diffusion. The principle of the method was that a nitrocellulose solution in acetone, methyl alcohol or amyl acetate diffused into a pure solvent layer on the surface of the solution. Clearly molecules of smaller size penetrate more rapidly. A nitrocellulose solution of 12.8% N was separated into two layers in this way after 42 days diffusion. The lower fraction comprised nitrocotton with a nitrogen content of 13.1% N, the upper layer one of 12.1% N. 

The chemist can try to separate the two isomers by careful fractional distillation but it will be next to impossible to do because both the cis and the trans have practically the same boiling point. There are a few things that the chemist can do or hope for to get rid of that cis isomer. The cis configuration is less stable than the trans and may switch over to the trans configuration with a little help. The chemist can gently heat the isosafrole oil to about 150°C for an hour or so. She can also try the same heating except have the oil mixed with some acetic acid. Also, the isosafrole can be fractionally distilled to ultra purity and then be allowed to simply sit for a couple of days. Trans isosafrole may spontaneously crystalize out while the cis form remains as an oil. They can then be separated by filtration. 

Next, by trial and error, we try to find a value for y such that sinh" y matches one of the 17/17 fractions in Table 2.2, say 17/17 = 0.80. This is easily done using either tables of sinh functions or the equation given in Table 2.1. The following results show that it is possible to place y within a range and then narrow that range without much difficulty. Remember, it is the inverse sinh values we are examining ... 

Tri-n-propylamine [102-69-2] M 143.3, b 156.5 , d 0.757, n 1.419, pK 10.66. Dried with KOH and fractionally distd. Also refluxed with toluene-p-sulfonyl chloride and with KOH, then fractionally distd. The distillate, after addn of 2% phenyl isocyanate, was redistd and the residue fractionally distd from sodium. [Takahashi et al. J Org Chem 52 2666 1987.]... 

Tri-n-butyi borate [688-74-4] M 230.2, b 232.4 , u 1.4092, d 0.857. The chief impurities are n-butyl alcohol and boric acid (from hydrolysis). It must be handled in a dry-box, and can readily be purified by fractional distillation, under reduced pressure. 

Tri-n-hexylborane [1188-92-7] M 265.3. Treated with hex-l-ene and 10% anhydrous Et20 for 6h at gentle reflux under N2, then vacuum distilled through an 18in glass helices-packed column under N2 taking the fraction b 130"/2.1mm to 137"/1.5mm. The distillate still contained some di-n-hexylborane [Mirviss J Am Chem Soc S3 3051 7967]. 

Dibydropteridine reductase (from sbeep liver) [9074-11-7] Mr 52,000 [EC 1.6.99.7]. Purified by fractionation with ammonium sulfate, dialysed versus tris buffer, adsorbed and eluted from hydroxylapatite gel. Then run through a DEAE-cellulose column and also subjected to Sephadex G-lOO filtration. [Craine et al. J Biol Chem 247 6082 1972.]... 

A very important analytical tool that is overlooked by many sourcetesting personnel is the microscope. Microscopic analysis of a particulate sample can tell a great deal about the type of material collected as well as its size distribution. This analysis is necessary if the sample was collected to aid in the selechon of a piece of control equipment. All of the efficiency curves for particulate control devices are based on fractional sizes. One would not try to remove a submicron-size aerosol with a cyclone collector, but unless a size analysis is made on the sampled material, one is merely guessing at the actual size range. Figure 32-8 is a photomicrograph of material collected during a source test. 

For orientation in trying to conti ol fractionators, it is w ell to emphasize the territory within which fractionators, and therefore control, move. 

This process removes the coarser fractions in the hydrocyclones. Hydrocyclones basically operate within the sand region, and if there is material that is finer than sand (material that passes a 200 mesh screen), then approximately 100 percent of that material will pass out the top. The finer fractions and the wastewater that overflow from the hydrocyclone are not treated any further. The contaminants that reside on the finer fhactions adhere fairly well to such particles, therefore, it does not make any processing sense to try and remove them. The coarser fractions then subsequently move down into the next cells. The fluid movement from right to left and the solid... 

In order to get the best out of fibre reinforcement it is not uncommon to try to control within close limits the fibre content which will provide maximum stiffness for a fixed weight of matrix and fibres. In flexure it has been found that optimum stiffness is achieved when the volume fraction is 0.2 for chopped strand mat (CSM) and 0.37 for continuous fibre reinforcement. 

Established OELs such as OSHA PELs and ACGIH TLVs, cover only a small fraction of the substances that are found in the workplace, and even for those chemicals discrepancies are commonly encountered among the different lists, For this reason, the European Union (EU) is trying an approach in which... 

A SEC material should be hydrophilic if it is to be used for biological applications. One such material, introduced by PolyLC in 1990 (8), is silica with a covalently attached coating of poly(2-hydroxyethyl aspartamide) the trade name is PolyHYDROXYETHYL Aspartamide (PolyHEA). This material was evaluated for SEC of polypeptides by P.C. Andrews (University of Michigan) and worked well for the purpose (Fig. 8.1). Because formic acid is a good solvent for polypeptides, Dr. Andrews tried a mobile phase of 50 mM formic acid. The result was a dramatic shift to a lower fractionation range for both Vq and V, (Fig. 8.2) to the point that V, was defined by the elution position of water. 

However, for quantities substantially less than this level, 7- to 10-mm i.d. analytical columns can often be used in a semipreparative mode. By repeatedly injecting 300 to 500 ju,l of up to 1% polymer, reasonable quantities of polymer can be isolated. An autosampler and automated fraction collector can be setup to perform such injections around the clock. Although the larger injections and higher concentrations will lead to a loss of resolution, in some situations the result is quite acceptable, with a considerable savings in time being realized over other means of trying to make the same fractionation. 

Point (1) is part of every new field there is not much you can do about it. If you want to live in another country, you have to learn the language. If you want to use computational chemistry methods, you need to learn the acronyms. I have tried in the present book to include a good fraction of the most commonly used abbreviations and standard procedures. 

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