Slow evaporation

Figure 7.9 shows a schematic representation of this effect, in which the ratio of the two isotopes changes with time. To obtain an accurate estimate of the ratio of ion abundances, it is better if the relative ion yields decrease linearly (Figure 7.9) which can be achieved by adjusting the filament temperature continuously to obtain the desired linear response. An almost constant response for the isotope ratio can be obtained by slow evaporation of the sample, viz., by keeping the filament temperature as low as is consistent with sufficient sensitivity of detection (Figure 7.9). 

In oaken battels, slow evaporation of water and alcohol through the staves is ordinarily compensated for by refilling and topping each battel by... 

Mineral spirits, a type of petroleum distillate popular for use in solvent-based house paints, consist mainly of aUphatic hydrocarbons with a trace of aromatics. This type of solvent finds use in oil- and alkyd-based house paints because of its good solvency with typical house paint binders and its relatively slow evaporation rate which imparts good bmshabiUty, open-time, and leveling. Other properties include lower odor, relatively lower cost, as well as safety and health hazard characteristics comparable to most other organic solvents. 

Using hexamethylphosphoramide as the solvent, only the second reaction occurs. Disilane also reacts with potassium in 1,2-dimethoxyethane to form KS1H3, although S1H4 and nonvolatile polysHanes are also produced (28,31). Pure crystalline KSiH prepared from SiH and potassium in 1,2-dimethoxyethane has been obtained by slow evaporation of the solvent. WhenHquid ammonia is used as the solvent, only a small fraction of SiH is converted into metal salt most of the SiH undergoes ammonolysis (32). 

Basic teUurium sulfate 2 Te02 S03 [12068-84-8], 2 Te02 Se03 selenate and teUurate, 2 Te02 Te03, are known. The sulfate is made by the slow evaporation of a Te02 solution in H2SO4. It is stable up to 440—500°C and is hydrolyzed slowly by cold, and rapidly by hot water. 

Isobutyl isobutyrate, the Tischenko condensation product of two molecules of isobutyraldehyde, is a slow evaporating ester solvent that has been promoted as a replacement for ethoxyethyl acetate. Although produced primarily by the acetylation of isobutyl alcohol, some isobutyl acetate is produced commercially by the crossed Tischenko condensation of isobutyraldehyde and acetaldehyde. Isobutyl acetate [110-19-0] is employed mainly as a solvent, particularly for nitrocellulose coatings. 

Compared with ethyl acetate and isopropyl acetate, propyl acetate has slow evaporation rate and good solvent power which promote improved flow and leveling characteristics in a variety of coating formulations. 

Lead diethyidithiocarbamate [17549-30-3] M 503.7, pKj 3.36 (for A,A-diethyldithio-carbamate). Wash with H2O and dry at 60-70°, or dissolve in the min vol of CHCI3 and add the same vol of EtOH. Collect the solid that separates and dry as before. Alternatively, recryst by slow evaporation of a CHCI3 soln at 70-80°. Filter the crystals, wash with H2O until all Pb ions are eluted (check by adding chromate) and then dry at 60-70° for at least lOh. [Justus Liebigs Ann Chem 49 1146 1977.]... 

Neodynium nitrate (6H2O) [16454-60-7] M 438.4, m 70-72°. Crystallises with 5 and 6 molecules of H2O from cone solutions in dilute HNO3 by slow evaporation 1 part is soluble in 10 parts of H2O. 

Because of its regularity it would be expected that the polymer would be capable of crystallisation. In practice, however, the X-ray pattern characteristics of crystalline polymer is absent in conventionally fabricated samples. On the other hand films which have been prepared by slow evaporation from solvent or by heating for several days at 180°C do exhibit both haziness and the characteristic X-ray diagram. The amount of crystallisation and the size of the crystallite structures decrease with an increase in the molecular weight of... 

Metal island films form spontaneously during slow evaporation of the metal on to supports with low adhesion. The metal islands can produce the surface-enhancement required for Raman characterization of the surface of the support. 

The increase of restrictive regulations on the use of organic solvents favoured the increasing use of latex-based adhesives. Because of the slow evaporation of water, these adhesives show less tack and can suffer bacterial attack. Infrared heaters and ovens can be used to favour the evaporation of water. Often a small amount of solvent (coalescing aid) is added to the latex system to improve wetting and coalescence of the latex particles. 

Solvents. NBRs are soluble in aromatic hydrocarbons, chlorinated hydrocarbons, ketones, esters and nitroparaffin compounds. Solvents with high evaporation rate are acetone, methyl ethyl ketone, chloroform and ethyl acetate, among others. Solvents with slow evaporation rate are nitromethane, dichloropentenes, chloro-toluene, butyl acetate and methyl isobutyl ketone. 

Crystalline barium bromite Ba(Br02)2-H20 was first isolated in 1959 it can be made by treating the hypobromite with Br2 at pH 11.2 and 0°C, followed by slow evaporation. Sr(Br02)2.2H20 was obtained similarly. 

Methyl-heptenone also forms a bromine derivative which is well suited for the identification of the ketone. This body, which has the formula CgHjjBrgO. OH, melts at 98° to 99°, and is obtained as follows Three grams of methyl-heptenone are mixed with a solution containing 3 grams of caustic soda, 12 grams of bromine, and 100 c c. of water. After a time an oily substance is deposited, which is extracted with ether. The solvent is evaporated, and the residue, redissolved in ether, is treated with animal charcoal and filtered. On slow evaporation the product is obtained in well-defined crystals. 

Slow evaporation of a solution of 4 in carbon disulfide gives the orange ten-membered heterocycle 6.39 ... 

Peptoids based on a-chiral aliphatic side chains can form stable helices as well [43]. A crystal of a pentameric peptoid homooligomer composed of homochiral N-(1-cyclohexylethyl)glycine residues was grown by slow evaporation from methanol solution, and its structure determined by X-ray crystallographic methods. In the crystalline state, this pentamer adopts a helical conformation with repeating cis-... 

By using the same procedure, but with slow evaporation of the solvent, well-defined FCC supra-crystals made of nanoparticles are observed (Fig. 4) [44]. 

The first structurally characterized example of a platinum(II) derivative containing a saturated tetraamine macrocycle, 6,13-dimethyl-l,4,8,ll-tetraazacyclotetradecane-6,13-diamine has been reported (80).251 The species crystallizes as the colorless tetra-cationic complex from dilute HC104 solution by slow evaporation, where the two pendant primary amines are protonated. Other macrocyclic tetraamine complexes including [Pt([14]aneN4)]Cl2 have also been described.252... 

---