Dehydrating press

The advantage of dehydrating nitrocellulose with alcohol lies in the fact that any residual alcohol may be subsequently included in the solvent. The amount of residual alcohol in nitrocellulose depends not only upon the pressure applied in the dehydration press, but also on the type of nitrocellulose, i.e. it is somewhat larger in more highly nitrated nitrocellulose. Nitrocellulose made from wood cellulose swells in alcohol more readily than that made from cotton which is why the former retains more alcohol and more water. 

Figure 73. Smokeless Powder Manufacture. (Courtesy E. I. du Pont de Nemours and Company, Inc.) Dehydrating Press. The nitrocellulose comes from the dehydrating press in the form of a cylindrical block, impregnated with alcohol, ready for the mixer where ether is added and where it is colloided.

An infrared vibration band at 7.32 p, which appears on the dehydrated, pressed sihca-alumina catalyst, soaked with liquid triphenylcarbinol, PhjCOH, has been assigned to the Ph3C+ cation, the adsorbent acquiring a yellow coloration (90). 

Metallic sodium. This metal is employed for the drying of ethers and of saturated and aromatic hydrocarbons. The bulk of the water should first be removed from the liquid or solution by a preliminary drying with anhydrous calcium chloride or magnesium sulphate. Sodium is most effective in the form of fine wire, which is forced directly into the liquid by means of a sodium press (see under Ether, Section II,47,i) a large surface is thus presented to the liquid. It cannot be used for any compound with which it reacts or which is affected by alkalis or is easily subject to reduction (due to the hydrogen evolved during the dehydration), viz., alcohols, acids, esters, organic halides, ketones, aldehydes, and some amines. 

Carbon dioxide is ordinarily dehydrated duriag the Hquefactioa cycle to preveat free2e-ups ia the coadeaser and flow valves ia the Hquid lines. Ia some cases brittie or cmmbly blocks of dry ice have beea formed. This difficulty has beea overcome either by varyiag the residual moisture coateat of the Hquid carboa dioxide, or by injecting minute quantities of colorless mineral oil or diethylene glycol iato the Hquid carboa dioxide entering the press. If the dry ice is to be used for edible purposes, the additive must meet FDA specificatioas. 

The stabilised nitrate may then be bleached with sodium hypochlorite, centrifuged to remove much of the water in which the polymer has been slurried and dehydrated by displacement with alcohol while under pressure in a press. It is interesting to note that in these processes approximately 35 000 gallons (160000 litres) of water are used for every ton of cellulose nitrate produced. Control of purity of the water is important in particular the iron content should be as low as 0.03 parts per million since iron can adversely affect both the colour and heat stability of the polymer. 

The fi-compound is dissolved in 50 c c. pure dry ether, and dry hydiogen chloride is passed in with constant shaking to prevent the delivery tube from becoming blocked. Colourless crystals of the hydrochloride of the /3-o ime separate and aie filtered and washed with dry ether and then placed in a separating funnel and covered with a layer of ether. A. concentrated solution of sodium carbonate is gradually added with constant shaking until no further effervescence is observed. Sodium chloride is precipitated and the /3-oxime dissolves in the ether. The ether extract is sepaiated, dehydrated over sodium sulphate, and the ether remoi ed as rapidly as possible at the ordinary temperature by evaporation in vacuo. The residue crystallises, and when pressed on a porous plate leaves a mass of small silky needles, m. p. 126—130A It may be re-... 

V sol in acetic acid, ethanol and w. Prepn is by dehydration of propan-2-ol over Al oxide at 330°. It is also obtd as a pyrolysis product of propane and as a fraction of petr well head gases Propene has a Qc of 460.47kcal/mole the expln limits with air are 2.0 to 11.1% (Ref 2) it has an autoign temp of 927°F. Under unusual conditions, such as 955 atms press and... 

Isothermal a—time curves were sigmoid [1024] for the anhydrous Ca and Ba salts and also for Sr formate, providing that nucleation during dehydration was prevented by refluxing in 100% formic acid. From the observed obedience to the Avrami—Erofe ev equation [eqn. (6), n = 4], the values of E calculated were 199, 228 and 270 kJ mole"1 for the Ca, Sr and Ba salts, respectively. The value for calcium formate is in good agreement with that obtained [292] for the decomposition of this solid dispersed in a pressed KBr disc. Under the latter conditions, concentrations of both reactant (HCOJ) and product (CO3") were determined by infrared measurements and their variation followed first-order kinetics. 

Bourdon B, Turner S, Dosseto A (2003) Dehydration and partial melting in subduction zones constraints from U-series disequilibria. J Geophys Res (in press). 

The nitrocellulose is first dehydrated, that is the water present is replaced by alcohol. This is done by compressing the wet nitrocellulose in a hydraulic press and passing alcohol through the press until the strength in the block is about 92%. The resulting block of alchohol wet nitrocellulose is broken down to small pieces with toothed rolls. 

Fig. 26. (a) The ESR spectrum of lsNO on dehydrated 7-alumina (b) theoretical spectrum that resulted from the summation of the six curves (amplitude reduced) iu (c) (c) six equally spaced ESR spectra of 15NO on MgO (j 0) with permission Academic Press. 

The pure product is produced by dissolving the gum from the seeds in hot water. Diatomaceous earth filtration is then used to purify the solution. As the gum is less soluble in alcoholic than aqueous solutions it is precipitated by adding propan-2-ol. The pressed filter cake is then washed in pure alcohol to dehydrate it. The alcohol is then recovered by pressing again. The pressed product is then milled to the required final size. 

Dalla Rosa, M., Bressa, F., Mastrocola, D., and Pittia, P. 1995. Use of osmotic treatments to improve the quality of high moisture minimally processed fruits. In Osmotic Dehydration of Fruits and Vegetables (A. Lenart and P.P. Lewicki, eds), pp. 69-87. Warsaw Agriculture Univ. Press, Warsaw, Poland. 

Ishikawa, M. and Nara, H. 1993. Osmotic dehydration of food by semipermeable membrane coating. In Advances in Food Engineering (R.P. Singh and M.A. Wirakartakusuman, eds), pp. 73-77. CRC Press, London. 

Lazarides, H.N., Fito, P., Chiralt, A., Gekas, V., and Lenart, A. 1999. Advances in osmotic dehydration. In Processing Foods, Quality Optimisation and Process Assessment (A.R.F. Oliveira and J.C. Oliveira, eds), pp. 175-199. CRC Press, London. 

Salvatori, D., Andres, A., Chiralt, A., and Fito, P. 1997. Concentration profiles in apple tissue during osmotic dehydration. In Engineering and Food (R. Jowitt, ed.), pp. G77-G80. Sheffield Academic Press, Sheffield, UK. 

Griebenow, K. and Barletta, G., Dehydrated protein powders as hiocatalysts in nonaqueous solvents. In Lyophilization of Biopharmaceuticals (Biotechnology Pharmaceutical Aspects), Costantino, H.R. and Pikal, M.J. (eds). AAPS Press Arhngton, VA, 2004, pp. 643-668. 

FIGURE 23. Overall volume profile for the CA catalyzed hydration of CO2 and dehydration of HC03. Adapted from Reference 242. Copyright (1996) Academic Press Elsevier... 

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