Fractionation of nitrocellulose

Long ago it has been established that nitrocellulose is not a homogeneous substance. The earliest experiments in this field were made by Stepanov [100] who used the method of fractional precipitation from an acetone solution by the addition of water. Stepanov added different amounts of water stepwise to a solution of nitrocellulose in acetone to obtain fractions varying slightly, corresponding with the nitrogen content. The first and least soluble fraction contained 13.15% of nitrogen, while the N-content of the last, fifth portion, was 12.90%. 

Duclaux et al. [101] came to other conclusions for he established that particular fractions differed only in the viscosity of solutions the nitrogen content being the same. In order to precipitate nitrocotton from its acetone solutions the authors added acetone-water mixtures, richer and richer in water until finally pure water was added. A range of fractions was separated from nitrocellulose acetone solution of viscosity 0.1 P (poises). The viscosity of the first fraction was 0.603 P, and that of the last 0.007 P (2% solutions). 

Identical results of fractionating nitrocellulose by successive dissolution and precipitation have also been reported by other authors, e.g. Brunswig [102] Kumi-chel [103], Lacape [55], Glikman [104]. 

The most extensive investigations were those of Medvedev [105]. Commercial collodion cotton of 11.08%N was divided by Medvedev into four fractions. The viscosity of the acetone solutions as well as the molecular weight (osmotic method) of these were determined. The nitrogen content in all the fractions was approximately the same (Table 57). 

Lipatova and Lipatov [106] also found that the fractions, of higher viscosity possessed a higher temperature coefficient of viscosity. 

Fraction Nitrogen content % Specfic viscosity of solution of concentration Molecular weight (by osmotic pressure) 

---

The fractionating of nitrocellulose by chromatographic absorption has also been described. As reported by Claesson [116] a 1.5% nitrocellulose solution in... 

Alcohol from dehydration contains a certain quantity of nitrocellulose, i.e. its soluble fractions, mostly degraded, and a certain amount in suspension. Experiments have shown that about 2.2 g of dissolved nitrocellulose and 1.3 g of nitrocellulose in suspension—a total 3.5 g—occur in 11. of 70% alcohol from centrifuges. Sometimes however, the content of nitrocellulose in the alcohol may reach 10-12 g/1. 

Nitrocellulose granules, partially colloided, of sizes ranging from a few microns to a fraction of millimetres are suggested. The best known of the described methods was developed by the Hercules Powder Company [54]. It uses densified nitrocellulose originally developed for the lacquer industry, with an average particle size of 0.25 mm. 

The solubility of nitrocellulose in a solvent is defined by the percentage in this nitrocellulose of the fraction soluble in the solvent in question. 

In more recent experiments, Edelmann [95] has followed the depolymerization of nitrocellulose in dilute (0.5%) solution. He reported that nitrocellulose of an average polymerization degree n = 1060, and containing considerably amounts of the n > 2500 fraction, was degraded after being subjected for 1 and 4 hr to the action of ultrasonic waves of 800 kc/sec to an average polymerization degree of n = 910 and 630 respectively. By fractionation, the presence of a small quantity of n = 1400 was established in the latter. 

In other experiments, the opposite method of fractionation by dissolution was applied. In this way G. Meissner [107] prepared a soluble fraction with a nitrogen content of 10.28%, in quantity about 4% by extracting a specimen of nitrocellulose with 12.17% N using 50 50 ether-alcohol. The insoluble part was composed of nitrocellulose of 12.32% N. 

Extensive research into the fractional partition of nitrocellulose by means of acetone-water mixtures was carried out by Rogovin and Glasman [111]. The results of these experiments are given in the Table 59. 

Fig. 108. Chromatographic separation of nitrocellulose fractions (quantity of fractions in mg/g and their molecular weight Af Claesson [116]).

Thaw the 500-pL fraction for the first immunization and add 1.5-2 mL of PBS to reduce the concentration of nitrocellulose powder. 

For some time nitro-solvent-naphtha was a widely used component of explosive compositions. Liquid fractions of the nitrated substance have also been used in the manufacture of mining explosives and even of smokeless powder, as an explosive solvent for nitrocellulose. In the latter case liquid nitro-solvent-naphtha acted as a substitute for part of the nitroglycerine. This type of smokeless powder was also manufactured in Poland in the period between the two World Wars (Karda-szewicz, Markiewicz and Smisniewicz [34]). 

In this experiment, you will identify the C-terminal domain of glutathione-S-transferase (GST) from Schistosomajaponicum (purified from an Escherichia coli cell extract in Experiment 10) through the use of a Western blot. After the proteins present in the crude cell extract, unbound fraction, and the fraction eluted from the glutathione Sepharose resin are separated by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), the proteins will be electrophoretically transferred to a polyvinylidene fluoride (PVDF) membrane (Fig. 18-1). Although membranes composed of nitrocellulose or nylon can also be used for Western blotting, PVDF membranes are particularly effec-... 

The formation of starch complexes with other polysaccharides is perhaps best evidenced by the sorption of starch on cellulose and its derivatives. This sorption is selective with respect to amylose and amylopectin.1065 1066 Cotton fibers selectively adsorb amylose and not amylopectin.1667-1071 However, this method cannot be used for starch fractionation because cotton was considered to induce degradation (hydrolysis).1067 On the other hand, a method of purifying amylopectin that involves sorption of amylose on defatted cellulose has been published.1072 Reversible adsorption of amylopectin on cellulose occurs when starch is equilibrated with urea in 32-35% ethanol. There are also published attempts to separate starch components on filter paper.1073-1076 The reverse idea is applied in the stabilization of nitrocellulose by its sorption on starch.1077... 

Moltzer. Benoit and Doty (45) undertook the task of fractioning samples of nitrocellulose with 13.8-14.1% N. -llexane was added dropwise while stirring to 0.2% solution of nitrocellulose in acetone and several fractions were obtained. Their molecular weight was determined by light scattering, viscosity and osmotic pressure measurement. 

Measuremem of viscosity gave low er figures. The above results were confirmed by Hunt. Newman, Scharaga and Flory 4 1. Their figures for tfie molecular w eight of fractions w-ere lower 575 000 40 000. Canadian workers 4S obtained figures of 2 500000 650000. Their method of fractionation consisted in adding water to the solutior of nitrocellulose in acetone [49]. 

---