Steam distillation direct method

The reaction is carried out in a 2-litre long-necked round-bottomed flask, to which is fitted an efficient reflux water-condenser, capable of condensing a sudden rush of vapour without choking. For this purpose, a long bulb-condenser, similar to that shown in Fig. 3(A) (p. 9) is best, but the inner tube must be of wide bore (at least 12 mm.). Alternatively, an air-condenser of wide bore may be used, an.d a short double-surface water-condenser fitted to its top. A steam-distillation fitting for the flask should also be prepared in advance, so that the crude product can subsequently be steam-distilled directly from the flask. The glj cerol used in the preparation must be anhydrous, and should therefore be dehydrated by the method described on p. 113. 

Direct Injection of Amines. In the course of developing methods for investigation of in vivo formation of NMOR and NPYR in rats treated with precursor amines and nitrite, it was necessary to determine the contamination levels of the amines by the nitrosamines. Spiegelhalder et al (32) reported the presence of nitrosamines in all secondary and tertiary amine samples which they examined, using vacuum steam distillation followed by extraction and GC-TEA determination. 

Much time can be saved by the use of the steam distillation apparatus described, especially when large quantities have to be handled. The above directions avoid the use of extraction methods, which not only consume more time but may lead to appreciable losses of material. If the downward condenser is of iron, the apparatus is even more. efficient and the time for the steam distillation is halved. 

Ref 3,pp 256 7) b)Direct Method in which a soln of sample is heated with coned soln of strong base(such as NaOH) in a distillation flask and the expelled ammonia is collected in a flask contg an excess of standard acid. Then the excess of acid is titrated with std NaOH or KOH soln(Ref l,p 637 Ref 2,p 493 Ref 3,pp 254-5) c)Indirect Method, in which the sample is boiled in a flask with a known excess of NaOH soln until all NH3 is expelled with the steam. Then the flask is cooled and the excess of NaOH is titrated with std acid(Ref 3, P 255)... 

As an alternative method of procedure, the following may be substituted for Steps 4 to 7 inclusive of the above process. After distilling the benzol, the tarry mass may be stirred directly with 2000 mL of hot 0.3 N NaOH with a mechanical stirrer. The suspension is chilled and the supernatant Liquid poured or siphoned off. Repetition of the extraction two or three times is advisable. The alkaline aqueous solution is then extracted five or six times with 400 mL portions of sulfuric ether, thus transferring the hormone to ether solution. After distillation of the ether the residue is steam distilled as long as a distillate other than water is obtained. The condensed water is removed by vacuum distillation and the small amount of dark tarry residue leached 5 times with 50 mL of hot 0.3 N NaOH. This solution is filtered and the filtrate extracted with sulfuric ether (100 mL, 6 times). The ether solution is distilled and the residue leached with cold 0.3 N NaOH using 20 mL five times. This alkaline solution is filtered and extracted with 50 mL of sulfuric ether five times. Upon distillation of the ether and solution of the residue in a small quantity of hot ethyl alcohol, the hormone separates in semi-crystalline balls which may be filtered off. A further quantity is obtained by adding 3 volumes of water to the alcoholic solution. It may be recrystallized from 25% aqueous ethyl alcohol or from 25% aqueous acetone or from any of the following chloroform, benzol, ethyl acetate, ethyl ether or petroleum ether. The final product consists of colorless crystals which, when crystallized from dilute alcohol, possess a distinct rhomboid outline. The crystals melt at 242-243°C (248-249°C corrected) with some decomposition. 

A clear distinction between medicine and perfumery was not drawn until around 1800. In the previous centuries the main purpose of pleasing and beneficial fragrances was seen as warding off and curing the illnesses caused by noxious emanations. Today steam distillation is still one of the most important methods of producing natural perfumery materials. Some essential oils, such as those which occur in the skins of citrus fruits, are more usually produced by direct expression from the plant material. 

Distillation techniques, such as steam distillation, are typically carried out in a rotary evaporator after the sample has been solubilized in an organic solvent. The distillate is injected directly onto a suitable GC column. This method is used widely due to its simplicity and because components with high boiling points are recovered easily. High-vacuum distillation is used widely to isolate volatile components from solvent extracts. This procedure often requires an extraction step to remove water. 

In most cases, the crude imino chloride is treated directly by adding it to a solution of stannous chloride saturated with dry hydrogen chloride the aldehyde is then liberated by steam distillation. The procedure is illustrated by the synthesis of o-tolualdehyde (70%). Imino chlorides have also been prepared by treatment of ketoximes with phosphorus penta-chloride, viz., RR C NOH — RCC1=NR, in preparations of benzalde-hyde and p-chlorobenzaldehyde (70-85%). As in the Stephen reaction (method 164), groups ortho to the imino chloride group hinder the reaction. 

The realization that high yields can be obtained under the driving conditions of the steam distillations described in this paper suggests that other and equally simple methods for aldehyde removal may achieve the same high yields. Research in this direction could prove rewarding, particularly where the aldehyde products are not steam distillable or where the ozonolysis intermediates may require special conditions for their conversion to aldehydes. Even more intriguing for future research, however, is the verification or disproof of the mechanisms proposed here. 

This method has been used to prepare nanoemulsions of such polymers as cellulose esters and epoxy resins, similar to latexes produced by emulsion polymerization. The nanoemulsions are prepared by direct emulsification of solutions of the polymers in organic solvents, followed by removal of the organic solvent by steam distillation under reduced pressure. The nanoemulsions produced in this fashion had stabilities > 1 year. 

This chapter discusses some more recent variations of methods for isolation of volatiles fiom food and plant materials. For particular problems there are advantages to each of the three main types of isolation methods, direct extraction, steam distillation and dynamic headspace. Direct solvent extraction is the only method which is reasonably efficient in isolating components of both high and low water solubility. Because food and plant volatiles are usually water soluble at their ppm concentrations their isolation by steam distillation does not fit the theory s required non-miscible conditions and this may be better considered a type of dynamic headspace isolation. By atkpting ideas fiom a recently published direct solvent extraction metiiod, which used excess sodiiun fate to bind all water in aqueous foods, the authors discovered an effective dynamic headspace meAod for isolating Furaneol and other water soluble volatiles. 

An advantage of the direct extraction method (3-6) is that volatiles of both low and high water solubility are isolated in one operation. Other commonly used methods such as steam distillation or dynamic headspace are not effective in isolating highly water soluble compounds such as Furaneol or maltol fiom mostly aqueous food and plant materials whereas these compounds can often be isolated efficiently by direct solvent extraction. 

Peak numbers correspond to those in Figures i and 2 and Table II. RI, retention index. Average relative conccniratiop t. standard deviation (n=I2). SDE, simultaneous steam distillation-solvent extraction. DE, direct solvent extraction. Compound tentatively identified by comparing its mass spectrum to Wiley 13SK mass spectral database, Compound not previously identified in saffron. Compound positively identified as described in materials and methods. V trace. Compound tentatively identified by comparing its mass spectrum with published literature (II). nd. not detected. I.S., internal standard, N/A, not available, peak could not be resolved. 

As has been previously said, 2,3-butanodione (diacetyl) is an important aroma of alcoholic beverages, it has not been studied and measured extensively in the past because of analytical difficulties in the quantitation caused by its highly volatile nature, chemical instability, and interference of other compounds. Colorimetric methods to measure diacetyl have been widely used in the past. These methods involve steam distillation to isolate diacetyl from the matrix. However, distillation has the disadvantage of incomplete isolation of diacetyl from other closely related compounds that will result in an overestimation of its concentration. A fluorometric method was developed to improve upon the lengthy distillation methods that involve derivatization. Although acetaldehyde and its acetal can be determined by direct injection GC-FID in spirit drinks (EU reference method for spirits), most chromatographic methods for minor aldehydes implicate also derivatization. While a very sensitive and accurate method based on SMPE without derivatization and MS detection has been developed, it requires the use of... 

There are a variety of methods in which the alcohol content of a wine may be determined, which may be as Table 1 shows, loosely divided into direct and indirect methods. The latter involves prior separation of the alcohol by distillation, usually by steam distillation, whereas the direct methods may be carried out on wine without any sample pretreatment. Within both categories there exist both physical, and less widely used, chemical methods. 

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