Distillation fractions specific gravity

It is common that a mixture of hydrocarbons whose boiling points are far enough apart petroleum cut) is characterized by a distillation curve and an average standard specific gravity. It is then necessary to calculate the standard specific gravity of each fraction composing the cut by using the relation below [4.8] ... 

It is worthwhile to mention that the distribution of naphthenic acids is not uniform in a crude oil since a maximum value is observed in the fractions distilled between 400 and 450°C and whose average specific gravity is 0.950 (Figure 8.2). 

The different cuts obtained are collected their initial and final distillation temperatures are recorded along with their weights and specific gravities. Other physical characteristics are measured for the light fractions octane number, vapor pressure, molecular weight, PONA, weight per cent sulfur, etc., and, for the heavy fractions, the aniline point, specific gravity, viscosity, sulfur content, and asphaltene content, etc. 

It is possible to calculate the properties of wider cuts given the characteristics of the smaller fractions when these properties are additive in volume, weight or moles. Only the specific gravity, vapor pressure, sulfur content, and aromatics content give this advantage. All others, such as viscosity, flash point, pour point, need to be measured. In this case it is preferable to proceed with a TBP distillation of the wider cuts that correspond with those in an actual refinery whose properties have been measured. 

These specifications include specific gravity, maximum water content, maximum values for toluene- or ben2ene-insoluble material, and maximum amounts distilling at 230°C, 270°C, 315°C, and 355°C. In the case of the AWPA specifications, there are minimum limits to the specific gravities of each of the distillate fractions in the case of the WEI specifications, limits for the contents of ben2o[a]pyrene and water-soluble phenols (tar acids). 

U has more recently been found that amyrol, like santalol, is not a uniform body, hot that hv frequently repeated fractional distillation It can be separated into dilTereot alcohols. The higher boiling, very viscons compound has a faint, chnrscterlslic, fragrart odour ica formula Specific gravity ahont 0 937 or = about + 36" ... 

In 1899 Thoms isolated an alcohol from Peru balsam oil, which he termed peruviol. This body was stated to have powerful antiseptic properties, but has not been further investigated until Schimmel Co. took up the subject. The oil after saponification was fractionated, and after benzyl alcohol had distilled over, a light oil with characteristic balsamic odour passed over. It boiled at 125° to 127° at 4 mm., and had a specific gravity 0 8987, optical rotation -1- 12° 22, and refractive index 1-48982. This body appeared to be identical with Hesse s nerolidol, whilst in physical and chemical properties it closely resembles peruviol. The characters of the various preparations were as follows —... 

The specific gravity, refractive index, and specific rotation given above are those recorded by Paolini and Divizia and are probably accurate since the a-santalol was prepared by regeneration from its strychnine phthalate. The values recorded for commercial santalol, prepared by fractional distillation, are as follows, and are the average values for the mixed santalols as they occur in sandalwood oil... 

The value of fractional distillation in the examination of essential oils cannot be overestimated. The various fractions may be examined and their specific gravities, optical rotations, and refractive indices determined. The combination of these figures will often give the experienced analyst the most useful information and save him many hours needless work. Experience alone, however, will teach the chemist to make the fullest use of the results so obtained. In most cases distillation under reduced pressure is necessary on account of the risk of decomposing the various constituents of the oil. The use of a Briihl receiver (or any similar contrivance), which is easily obtained from any apparatus maker. 

Petroleum or mineral oil (kerosene, etc.) are less soluble in alcohol than most oils. They have a low specific gravity and refractive index, and are not saponified by alcoholic potash. The lower boiling fractions can usually be detected by their odour, and the higher boiling fractions remain in the residue on fractional distillation. They are unaffected by fuming nitric acid. 

One classification method treats a large molecule as aromatic if it has a single benzene ring regardless of the other content. Another method considers the fraction of each molecule that is aromatic, naphthenic, or paraffinic. Obviously, in either case the analysis procedure is tedious. A third classification method simply measures the specific gravities of several fractions separated by distillation and attempts to relate chemical structure to specific gravity. 

MYRISTIC ACID. [CAS 544-63-8]. Also called tetradecanoic acid, formula CHjlCHiJnCOOH, At room temperature, it is an oily, white crystalline solid. Soluble in alcohol and ether insoluble in water. Specific gravity 0.8739 (80°C) mp 54.4°C bp 326.2°C. Combustible. The acid is derived by the fractional distillation of coconut oil. Myristic ucid is used in soaps cosmetics in the synthesis of esters for flavorings and perfumes and as a component of food-grade additives, Myristic acid is a constituent of several vegetable oils. See also Vegetable Oils (Edible). 

Trimethylene glycol occurs in the glycerin which is produced by fermentation. There is no harm in leaving it in glycerin which is to be used for the manufacture of explosives. It may however be separated by fractional distillation. When pure it is a colorless, odorless, syrupy liquid, specific gravity (x°/4°) 1.0526 at 18°. It mixes with water in all proportions and boils at atmospheric pressure at 21 i° without decomposition. At temperatures above 15° or so, it is oxidized rapidly by nitric acid or by mixed acid. It is accordingly nitrated at 0-10° under conditions similar to those which are used in the preparation of ethyl nitrate and other simple aliphatic nitric esters (except methyl nitrate). 

Oil of Turpentine.—This is a common adulterant for the volatile oils and is not always easy to detect. In most cases use is made of the specific gravity, fractional distillation and rotatory power, and the characters of oil of turpentine are described in Chapter IX (see also Oil of Lemon). 

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