Powder efficiency

Table I lists a variety of organic nonlinear materials which have appeared in the literature their relative powder efficiencies, absorption cutoffs and /3 values (if available) are also provided. These materials are "typical" only in that they represent results from the few classes of organic compounds investigated to date, yet they are instructive in that one learns which molecular properties may be important. A few caveats are in order to avoid misinterpretation of the data in Table I. Except for compound 10 (19) all the powder efficiency and cutoff data are from our own measurements. Powder measurements were performed on ungraded samples using the Nd YAG output at 1.06/t as fundamental since powder efficiency is a function of particle size distribution and a variety of other factors (3) these values are only semiquantitative. The cutoff values are the wavelengths for which 10-4M solutions in ethanol (unless otherwise indicated) have no absorbance. The cutoff values will be similar to those found in crystal state except where intermolecular charge transfer is important in the crystal or the molecule is solvatochromic, this latter effect being quite common for cyanine dyes such as...

The SHG efficiencies of more than 300 organometallic complexes measured using the Kurtz powder method have been reported, but most responses are either very low or zero. Table II contains data for samples with reported Kurtz powder efficiencies greater than or equal to twice that of urea, with Fig. 5 containing the structural formulas of complexes with very large (>50 X urea) responses. 

Complexes with Kurtz Powder Efficiencies a2 x Urea... 

An optimum aerodynamic particle diameter for lung delivery is considered to be 3 pm. Particles having aerodynamic size above 5 pm typically deposit in the upper part of the lung, which is not an efficient site for drug adsorption. Particles with aerodynamic diameter smaller than 1 pm can be expelled during exhalation. To deliver powders efficiently via inhalation, particles with defined size must be obtained and delivered. ... 

ApplicatiOTis of these molecular NLO chromophores, to produce second-order bulk NLO materials or structured Aims, are very limited. Actually, in spite of their veiy large molecular hyperpolarizabilities, they exhibit crystalline materials with modest bulk SHG efficiency [11], e.g., the most efficient crystalline material shows a powder efficiency of only eight times that of urea [11], in consequence of the reluctance of acetylide complexes to crystallize in noncentrosymmetric structures. 

Heat together under very efficient water reflux 1 g. of freshly fused dry powdered ZnClg, 2 ml. of diethyl ether and 0 5 g. of 3,5 -dinitrobenzoyl chloride for 2 hours. Shake the product with 5 ml. of water and ther add 10% NaOH solution until all the ZnCl, and excess of 3,5-dinitro> benzoyl chloride and 3,5-dinitrobenzoic acid have gone into solution. Filter at the pump and recrystallise from petroleum (b.p. 40-60°) to obtain ethyl 3,5-dinitrobenzoate, m.p. 93°. (M ps. of other 3,5 dinitro-benzoates, p. 536.)... 

Dissolve 200 g. of sodium nitrite in 400 ml. of water in a 2-litre beaker provided with an efficient mechanical stirrer, and add 40 g. of copper powder (either the precipitated powder or copper bronze which has been washed with a little ether). Suspend the fluoborate in about 200 ml. of water and add it slowly to the well-stirred mixture. Add 4-5 ml. of ether from time to time to break the froth. The reaction is complete when all the diazonium compound has been added. Transfer the mixture to a large flask and steam distil until no more solid passes over (about 5 litres of distillate). Filter off" the crystalline solid in the steam distillate and dry upon filter paper in the air this o-dinitrobenzene (very pale yellow crystals) has m.p. 116° (t.c., is practically pure) and weighs 29 g. It may be recrystallised from alcohol the recrystallised solid melts at 116-5°. 

In a 2 litre bolt-head flask, equipped with an efficient mechanical stirrer, place 60-5 g. (50 ml.) of pure nitrobenzene and a solution of 30 g. of ammonium chloride in 1 litre of water. Stir vigorously and add 75 g. of a good quality zinc powder (about 90 per cent, purity) in small portions over a period of 5 minutes. The main reaction occurs about 5 minutes after the addition and the temperature rises. When the temperature reaches about 65°, add enough ice to the weU-stirred mixture to reduce the temperature to 50-55°. Filter the solution through a Buchner funnel twenty minutes after the first portion of zinc powder was introduced wash the zinc oxide residues with 600-700 ml. of boiling water. 

Place 25 g. of methyl methacrylate polymer (G.B. Diakon (powder). Perspex (sheet) U.S.A. Lucite, Plexiglass) in a 100 ml. Claisen flask, attach an efficient condenser e.g., of the double smface type) and distil with a small luminous flame move the flame to and fro around the sides of the flask. At about 300° the polymer softens and undergoes rapid depolymerisation to the monomer, methyl methacrylate, which distils over into the receiver. Continue the distillation until only a small black residue (3-4 g.) remains. Redistil the hquid it passes over at 100-110°, mainly at 100-102°. The yield of methyl methacrylate (monomer) is 20 g. If the monomer is to be kept for any period, add 0 -1 g. of hydro quinone to act as a stabiUser or inhibitor of polymerisation. 

In the flask were placed 0.20 mol of the acetylenic alcohol, 0.24 mol of tosyl chloride and 350 ml of diethyl ether. The mixture was stirred at room temperature, until the solid had passed into solution and then cooled at -5 to -10 c in a bath of dry-ice and acetone. Machine-powdered KOH (130 g) was added with vigorous stirring, initially in relatively small portions [oa. 5 g), at intervals of 2 min. The reaction was strongly exothermic at first, and efficient cooling was necessary in order to maintain the temperature of the reaction mixture between -5 and O C... 

Note 2. Prepared by azeotropic removal of water from the commercial, water-containing product by means of benzene. This solvent was removed in a water--pump vacuum and the remaining mass was powdered. The water-containing acid appeared to work much less efficiently as catalyst. 

Powdered antimony pentoxide is used primarily in plastics. Stabilizers used to prevent the particles from growing are caustic, and can react with the halogen in the formulation. This can result in color formation and a lower flame-retarding efficiency of the system. 

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