Volume 1

Ure's dictionary of arts, manufactures, and mines : containing a clear exposition of their principles and practice / by Robert Hunt ; assisted by F.W. Rudler.

Date:
1875-1878
Catalogue details

Licence: Public Domain Mark

Credit: Ure's dictionary of arts, manufactures, and mines : containing a clear exposition of their principles and practice / by Robert Hunt ; assisted by F.W. Rudler. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    all of which are extremely odorous. No creosote found ia commerce is ever perfectly homogeneous, nor, in fact, is it ncCL-ssary that it should be so. JS perfectly soluble in potash and acetic acid of the density 1'070, and if it does not become coloured by exposiu-e to the air, it may be considered piu-e enough for all medicinal purposes. The oils from wood- and coal-tar may be made to j'ield creosote by the folloOTng process. The oils are to be rectified until the more volatile portions (which are lighter than water) have passed over. As soon as the product running from the still sinks in water the receiver is to be changed, and the oils may be received until the temperature required to send over the oil is as high as 480° F. The oil so obtained is to be dissolved in caustic soda, all iusoluble in it being rejected. The alkaline solution, after being mechanically separated, as far as possible, from the insoluble oil, is to be boiled for a very short time. Two advautngos are gained by this operation : any volatile bases become expelled, and a substance which has a tendency to become brown on keeping, is destroyed. Sometimes the oil on treatment with potash yields a quantity of a crystalline paste. This is naphthaline, and should be removed by filtration through coarse calico or canvas. The alkaline liquid is then to be supersa- turated with dilute sulphuric acid, on which the creosote separates and rises in the form of an oil to the siu'face. This creosote is already free from the greater number of impurities, and, if rectified, may be used for many purposes. To obtain a purer article the operations commencing with solution in caustic soda are to be repeated. If the alkaline solution on boiling again becomes coloured, the purification must be gone tlirough a third time. It is essential not to boil the alkaline solution long, or a serious loss of creosote would take place. According to Eeichenbach the boiling point of creosote is 397°. Carbolic acid boils between 369° and 370°. Cresylic acid boils at 397°. From this it would appear that Eeiehenbach's creosote consisted of cresylic acid. The specific gravity of creosote according to Eeichenbach is r037 at 68°, that of carbolic acid is 1-065 at 64°. Carbolic acid and its homologues, when mixed with quicklime and exposed to the air, yield a beautiful red colour, cvving to the formation of rosolic acid. See Disinfectants. CRESOXi. C'^H^O- (C'H^O). A compound found with carbolic acid in coal-tar, creosote, and the tar of pine-wood. CRESTXiXC ACID. C'^ffO^ (C'H^O). A homologue of carbolic acid. See Creosote : Disinfectants. CBXTK. ('cpiflr), a barleycorn). A unit of weight, introduced into modern che- mistry by Dr. Hofmann. A crith is the weight of a litre of hydrogen at 0°C. and 760 mm. bar. pressure ; this amounts to 0-089636 gramme. The use of the crith is convenient in calculating the weights of given volumes of different gases on the metric system. CROCXSOXiXTS. A fibrous asbestiform mineral occurring in the Griqua Country, South Africa. White, brown, red, and blue varieties are known ; and some of these, when cut en cahochon, resemble coloured cat's-eye, and are used in jewellery. Tlie true croeidolite is a hydrous silicate of protoxide of iron, magnesia, and soda; but much of the so-called croeidolite from South Africa has been proved to be pseudo- morphous fibrous quartz colom-ed with oxide of iron and other foreign matter. CROCOISXTE. Native chromate of lead, PbO.CrO^ (PbCrC) occm-ring in small liyacinth-red crystals in some of the Siberian mines, in Hungary, in Brazil, and in the Philippine Islands. It was in this mineral that the metal chromium was dis- covered in 1794, by Vauquelin. The name of the species is sometimes written, Crocoitc. CROCITS. The €ommercial name for a polishing powder made with oxide of iron. The older chemists gave this name to many of the metallic compounds, which had something of the nature of rust of iron. Crocus Martis, sesquioxide of iron ; Crocus Mctalloniin, liver of antimony, glass of antimony, oxysulphide of antimony; Crocus Veneris, oxide of copper. CROCVS. A genus of plants belonging to the natural order of Iridacee. The Crocus sativus is the species from which the saffron of commerce is produced. The stigmata of the flowers are of a deep orange colour, and these, when dried in the loose state, form hay sa§ron ; when compressed it forms the caJce saffron. Saffron is culti- vated in Cambridgeshire; it is also imported from Sicily, France, and Spain; but