CROTON OIL 1011 



all of which are extremely odorous. No creosote found iu commerce is ever perfectly 

 homogeneous, nor, in fact, is it necessary that it should be so. If perfectly soluble in 

 potash and acetic acid of the density 1'070, and if it does not become coloured by 

 I'.xposure to the air, it may be considered pure enough for all medicinal purposes. The 

 oils from wood- and coal-tar may be made to yield creosote by the following process. 

 The oils are to bo 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 bo received until the temperature 

 required to send over the oil is as high as 480 F. The oil so obtained is to bo 

 dissolved in caustic soda, all insoluble 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 advantages are gained by this operation : any 

 volatil bases become expelled, and a substance which lias 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 surface. This creosote is already free from the greater number 

 of impurities, and, if rectified, may bo 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 through a third time. It is essential not to boil the alkaline solution long, or a 

 serious loss of creosote would take place. According to Reichenbach 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 Keichenbach's creosote consisted of cresylic 

 acid. The specific gravity of creosote according to Reichenbach 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, owing to the 

 formation of rosolic acid. See DISINFECTANTS. 



CRESOXi. C U H 8 2 (C'H 8 O). A compound found with carbolic acid in coal-tar, 

 creosote, and the tar of pine-wood. 



CRESYX.XC ACID. C U H 8 2 (C 7 H 8 O). A homologue of carbolic acid. See 

 CREOSOTE ; DISINFECTANTS. 



CRXTH. (/cpi&Jj, 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 0C. 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. 



CROCXDOXiXTE. 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 cabochon, resemble coloured cat's-eye, and are used in jewellery. The 

 true crocidolite is a hydrous silicate of protoxide of iron, magnesia, and soda ; but 

 much of the so-called crocidolite from South Africa has been proved to be pseudo- 

 morphous fibrous quartz coloured with oxide of iron and other foreign matter. 



CROCOXSITE. Native chromate of lead, PbO,Cr0 3 (PbCrO 4 ) occurring in 

 small hyacinth-red crystals in some of the Siberian mines, in Hungary, in Brazil, and 

 in tlio 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, 

 Crocoite. 



CROCUS. The commercial 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 

 Metallorum, liver of antimony, glass of antimony, oxysulphide of antimony ; Crocus 

 Veneris, oxide of copper. 



CROCUS. A genus of plants belonging to the natural order of Iridacece. 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 saffron ; when compressed it forms the cake saffron. Saffron is culti- 

 vated in Cambridgeshire ; it is also imported from Sicily, France, and Spain ; but 

 English saffron is always preferred. 



CROSS COURSE. A mining term. See MINING. 



CROSS CUT. A mining term. See MINING. 



CROSS-FX.UCJLa.lTS or FX.OOJKAJTS. The name given by the Cornish 

 miners to clay veins crossing the mineral lodes. See FLOOKAN. 



CROTAItARXA JUNCEA. The plant which yields Sunn or Bengal hemp. 



CROTOIT OXXt. A powerful purgative oil, obtained from seeds of the Croton 

 T/afit'm, a shrub grown in India and the neighbouring isles. 



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