124 



GEISSLER'S TUBES 



GELATINE 



Ammon (Erl. 1826), Dachenx (Paris and Strasb. 

 1876), and Lindemann (Freiburg, 1877). 



Geissler's Tubes. See VACUUM TUBES. 



Gela, an ancient city on the southern coast of 

 Sicily, near the site of the modern Terranuova. 

 It was founded by a colony of Khodians and 

 Cretans, 690 B.C., and grew so rapidly that as early 

 as 582 it was able to found a colony at Agrigentum, 

 which was soon to outstrip Gela itself ( see GELON ). 

 Here ^Eschylus died and was buried, 456 BC.^nd 

 here Apollodorus was born. In 280 its inhabitants 

 were transplanted to Phintias. 



GelasillS, the name of two popes. GELASIUS 

 I., an African by birth, succeeded Felix III. in 

 492, and was one of the earliest bishops of Rome 

 to assert the supremacy of the papal chair, not 

 only over temporal authority, but also over general 

 councils of the church. He vigorously repressed 

 Pelagianism, which was spreading in Dalmatia, 

 renewed the ban of his predecessor against the 

 oriental patriarch, drove out the Manichaeans 

 from Rome, and died in 496. There are extant a 

 treatise of his against the Eutychians and Nes- 

 torians, De duabus in Christo natwris, several 

 letters, and a Codex Sacramentarius. GELASIUS 

 II., formerly John of Gaeta, was educated at the 

 Benedictine abbey of Monte Cassino, was cardinal 

 and chancellor under Urban II. and Paschal II., 

 and on the death of the latter in the June of 1118 

 was chosen pope by the party hostile to the Em- 

 peror Henry V. "The imperial party at Rome 

 under the Frangipani seized his person, but were 

 forced to set him free by the menacing attitude 

 of the mob. The new pope fled before the advanc- 

 ing imperial troops to Gaeta, where he first 

 received his consecration, and whence he fulmin- 

 ated the thunders of excommunication against 

 Hemy V. and Gregory VIII., the antipope he 

 had et up. Soon after he was able to return to 

 Rome, but ere long had to betake himself for pro- 

 tection to France, where he died in the monastery 

 of Clugny, early in 1119. 



Gelatine, in Chemistry. Little is yet defi- 

 nitely known of the chemical nature of gelatine. 

 It consists approximately of carbon 49 '6, oxygen 

 25 '4, nitrogen 18 '3, and sulphur about O'l per 

 cent. It is soluble in hot water, in acetic acid, and 

 in cold sulphuric acid, and is insoluble in alcohol, 

 ether, and other organic liquids ; the aqueous 

 solution is precipitated by tannic acid, chrome 

 alum, and corrosive sublimate, but not by most 

 acids, salts, or alkalies in dilute solution. Gelatine 

 may be purified by dissolving it in water and 

 pouring the solution into a large bulk of alcohol ; 

 the clot which forms consists of nearly pure 

 gelatine, containing only a trace of ash. By dry 

 distillation 'gelatine yields a quantity of carbonate 

 of ammonia, and a foul smelling brown oil contain- 

 ing carbonate, sulphide and cyanide of ammonia, 

 aniline, methylamine, picaline, and a number of 

 pyridine bases. Gelatine solution dissolves lime 

 and calcium phosphate much more freely than cold 

 water, forming with the latter a definite compound, 

 which probably forms part of the tissue of bones. 



In Technology, the term gelatine, although 

 usually applied to only one variety of the sub- 

 stance obtained by dissolving the soluble portion 

 of the gelatinous tissues of animals, nevertheless 

 properly belongs also to Isinglass (q.v. ) and Glue 

 (q.v.), which are modifications of the same 

 material. Vegetable jelly is also analogous. 

 Gelatine and glue signify the more or less pure and 

 carefully prepared jelly of mammalian animals ; 

 but the term isinglass is only applied to certain 

 gelatinous parts of fishes, which from their exceed- 

 ing richness in gelatine, are usually merely dried 

 and used without any other preparation than that 



of minute division for the purpose of facilitating 

 their action. 



Gelatine proper is prepared for commercial pur- 

 poses from a variety of animal substances, but 

 chieHy from the softer parts of the hides of oxen 

 and calves and the skins of sheep, such as the 

 thin portion which covers the belly, the ears, &c. ; 

 also from bones and other parts of animals. One of 

 the best, if not the best of the varieties of gelatine 

 manufactured in Great Britain, is the ' sparkling 

 gelatine ' of Messrs Cox of Gorgie, near Edinburgh, 

 which is remarkable for its great purity and 

 strength, or gelatinising power, and is purified by 

 processes patented by them. The materials they 

 use are carefully selected portions of ox only 

 imported from South America. Another prepara- 

 tion, made by Mackay of Edinburgh from calves'- 

 feet, is deserving of special mention. 



The general method adopted with skin-parings 

 or hide-clippings is first to wash the pieces very 

 carefully ; they are then cut into small pieces and 

 placed in a weak solution of caustic soda for a 

 week or ten days. When this process of digestion 

 has been sufficiently carried on, the pieces of skin 

 are then transferred to revolving cylinders supplied 

 with an abundance of clean cold water, and after- 

 wards are placed still wet in another chamber lined 

 with wood, in which they are bleached and purified 

 by exposure to the fumes of burning sulphur ; they 

 next receive their final washing with cold water, 

 which removes the sulphurous acid. The next 

 operation is to transfer them to the gelatinising 

 pots. Water is poured in with the pieces, and kept 

 at a high temperature by means of the steam in the 

 cases surrounding the pots. 



By this means the gelatine is quite dissolved out 

 of the skin, and is strained off whilst still hot ; it 

 is poured out in thin layers, which as soon as they 

 are sufficiently cooled and consolidated are cut 

 into small plates, usually oblong, and laid on 

 nets, stretched horizontally, to dry. It is then cut 

 into shreds and is ready for market. 



Another process, introduced by Mr Swineburne, 

 consists in treating pieces of calfskin by water 

 alone, without the soda and sulphur processes ; the 

 pieces, after simple washing, being transferred at 

 once to the pots to be acted upon by the steam. 

 Inferior gelatine is made from bones and other 

 parts of animals ; and it is understood that the 

 enormous number of rats killed in the sewers and 

 abattoirs of Paris are used by the gelatine-makers. 

 The French manufacturers succeed better than 

 any others in clarifying these inferior gelatines, 

 and they rarely make any others ; they run their 

 plates out very thin, which gives them greater 

 transparency ; and they colour them with most 

 brilliant colours, and form very fine-rolled sheets, 

 tempting the eye with an appearance of great 

 delicacy and purity. 



Gelatine sliould never be judged by the eye 

 alone. Its purity may be very easily tested thus : 

 soak it in cold water, and then pour upon it a small 

 quantity of boiling water ; if pure it will form a 

 thickish, clear, straw-coloured solution, free from 

 smell, but if made of impure materials it will give 

 off a very offensive odour, and have a yellow gluey 

 consistency. No article manufactured requires 

 such careful selection of material and such nice and 

 cleanly manipulation to ensure a good marketable 

 character ; and those anxious for purity should 

 avoid all artificially coloured varieties, however 

 temptingly got up, unless they are required for 

 merely decorative purposes and not for food. Of 

 late years the commercial uses have greatly 

 increased. Gelatine is the foundation of the dry- 

 plate system of photography, and by its means 

 the science has been revolutionised and its capabili- 

 ties extended to an extraordinary degree. To the 



