The process of extraction with volatile solvents is similar to that used in the extraction of oils and fats, but as only the most highly purified solvents can be used, this process has not yet gained commercial importance.
The employment of guncotton as a propellant was possible only after the discovery that it could be gelatinized or made into a colloid by the action of so called solvents, e.g.
That nothing analogous to bitumen exists in coals is proved by the fact that the ordinary solvents for bituminous substances, such as bisulphide of carbon and benzol, have no effect upon them, as would be the case if they contained bitumen soluble in these re-agents.
Though his writings abound in universal solvents and other devices of the alchemists, he made some real contributions to chemical knowledge.
Certain solvents, such as water, liquid ammonia or liquid hydrocyanic acid, possess the power of making some solutes, such as mineral salts and acids, when dissolved in them, conductors of electricity.
If it be desired to obtain larger quantities than are yielded by the above-described methods, processes having for their object the extraction of the seeds by volatile solvents must be resorted to.
Various solvents, such as benzene, alcohol and chloroform, will dissolve out the pigment, leaving the plastid colorless.
It crystallizes in prisms or leaflets which melt at 72-75°C. and are readily soluble in water and in all organic solvents except ligroin.
There is no feasible method at present known of preventing the inclusion of the resin of the latex with the rubber during coagulation, and although the separation of the resin from the solid caoutchouc by means of solvents is possible, it is not practicable or profitable commercially.
The best solvents for rubber are carbon bisulphide, benzol and mineral naphtha, carbon tetrachloride and chloroform.
The nitrates are also very insoluble substances, all the so-called solvents merely converting them into jelly.
They pass through a viscous stage in cooling from a state of fluidity; they develop effects of colour when the glass mixtures are fused with certain metallic oxides; they are, when cold, bad conductors both of electricity and heat, they are easily fractured by a blow or shock and show a conchoidal fracture; they are but slightly affected by ordinary solvents, but are readily attacked by hydrofluoric acid.
The theory most widely accepted at present is that glass is a quickly solidified solution, in which silica, silicates, borates, phosphates and aluminates may be either solvents or solutes, and metallic oxides and metals may be held either in solution or in suspension.
We can sometimes obtain definite compounds in a pure state by the action of appropriate solvents which dissolve the rest of the alloy and do not attack the crystals of the compound.
Equally good comparisons have been obtained for solutions in other solvents such as acetic acid 3.88, formic acid 2.84, benzene 5.30, and nitrobenzene 6.95.
The experiments of Raoult on solutions of organic bodies in water and on solutions of many substances in some dozen organic solvents have confirmed this result, and therefore the theoretical value of the osmotic pressure from which it was deduced.
Attempts have been made to co-ordinate this ionizing power of solvents with their dielectric constants, or with their chemical properties.
Solutions of colloids in solvents such as water and alcohol seem to be divisible into two classes.
It has been found, however, that molten cryolite and the analogous double fluoride represented by the formula Al 2 F 6.2NaF are very efficient solvents of alumina, and that these solutions can be easily electrolysed at about 800° C. by means of a current that completely decomposes the oxide but leaves the haloid salts unaffected.
Litharge and red lead are used in silver and gold assays, acting as solvents for silica and any metallic oxides present.
It is readily soluble in hot water and the ordinary organic solvents, but is only slightly soluble in cold water.
Another remarkable fact is that these substances yield coloured solutions in organic solvents; triphenylmethyl gives a yellow solution, whilst ditolylphenyl and tritolylmethyls give orange solutions which on warming turn to a violet and to a magenta, the changes being reversed on cooling.
Raoult (Comptes Rendus, 1886-87) employed other solvents besides water, and showed that the relative lowering for different solvents and different dissolved substances was the same in many cases for solutions in which the ratio of the number of gramme-molecules n of the dissolved substance to the number of molecules N of the solvent was the same, or that it varied generally in proportion to the ratio n/N.
Ink forms a large item in the total expenses of this department, besides which there are: oil for lubricating, turpentine and other solvents for cleaning, paper for proofs and making-ready, &c. When the work is printed it is handed to the warehousemen, who are responsible both for unprinted and printed paper.
Of these solvents, only the first three are of economic importance.
In leaching, the silver ore is subjected to the action of solvents, which dissolve the silver; from the solution the silver is precipitated and converted into a marketable product.
The leading solvents are aqueous solutions of thiosulphates, unsystematically but generally termed hyposulphites.
Of the other proposed volatile solvents ordinary ether has found no practical application, as it is far too volatile and hence far too dangerous.
At the present time the choice lies practically only between the two solvents, carbon bisulphide and naphtha (petroleum ether).
Yet even with naphtha traces of the solvents remain, so that the meal obtained cannot be used for cattle feeding, notwithstanding the many statements by interested parties to the contrary.
They behave similarly to solvents; and in their liquid condition leave a grease spot on paper.
It is readily soluble in hydrocarbon solvents, in chloroform and in alcohol.