54 



CELLULOID 



CELSIUS 



see also the articles BOTANY, CELL, TISSUES, LEAF, 

 BARK, &c. 



Celluloid, or PAEKESINE. This substance was 

 first made by Mr A. Parkes of Birmingham in 1855 

 or 1856. It chiefly consists of a dried solution of 

 gun-cotton (pyroxylin), or of what is nearly the 

 same thing, and oil. A variety of it can be made 

 with pyroxylin and camphor. It resembles ivory, 

 horn, tortoiseshell, and hardened india-rubber, as 

 regards certain properties. 



The pyroxylin is prepared by treating Cellulose 

 (q.v.) from such vegetable materials as cotton or 

 rlax waste, rags, paper-makers' half-stuff, or paper 

 itself, with a mixture of one part of strong nitric 

 acid and four parts of strong sulphuric acid. It is 

 convenient to call the product so obtained pyroxy- 

 lin, although the two things are not quite identical. 

 The distillate obtained by distilling wood naphtha 

 with chloride of lime is used as a solvent for 

 the pyroxylin, but other solvents, such as nitro- 

 benzol or aniline, and some camphor are added with 

 advantage. When the excess of solvent is removed 

 from the pyroxylin, it is mixed with a considerable 

 quantity of castor-oil or cotton-seed oil, and made 

 into a dough or paste between heated rollers. For 

 a hard compound the quantity of oil should be less 

 than the pyroxylin, for a soft one it should be 

 greater. Chloride of sulphur is sometimes added to 

 the oil. When articles made of celluloid are in a 

 partially manufactured state, they are soaked in 

 bisulphide of carbon or chloride of lime to remove 

 any trace of solvent, which would render them apt 

 to shrink if allowed to remain. Celluloid is of a 

 somewhat combustible nature unless the substances 

 used to colour it are such as will neutralise this, or 

 unless some non-combustible chemical, tungstate 

 of soda for example, is added to it. 



Properties and Uses. Celluloid has many valuable 

 properties. It is buff or pale brown in colour, but 

 it can be made as white as ivory, which it much 

 resembles, or manufactured in a transparent state. 

 It can be moulded or pressed into any form, and 

 turned, planed, or carved. Neither the atmosphere 

 nor water affects it. It is elastic and can be united 

 by its own cement. In a plastic condition celluloid 

 can be spread on textile fabrics, or it may be made 

 as hard as ivory, for which it is largely used as a 

 substitute. Billiard-balls, piano-keys, and combs 

 are made of it, the latter two articles extensively. 

 It can be coloured to represent amber, tortoiseshell, 

 or malachite. In imitation of red coral it has been 

 a good deal used for jewelry. Like vulcanite, 

 which it excels in durability but exceeds in price, 

 it has very numerous applications. We need only 

 mention umbrella-handles, brush-backs, knife- 

 handles, buttons, napkin-rings, card-cases, thim- 

 bles, and dolls. It is useful for optical instru- 

 ments, for cases for artificial teeth, and for some 

 surgical instruments. One special application of 

 it is for shirt fronts and collars. It is rised for very 

 pretty imitations of ivory, amber, tortoiseshell, 

 coral, malachite, &c. Some important develop- 

 ments in the manufacture and application are due 

 to J. W. Hyatt, of Newark, New Jersey. 



Cellulose is the substance secreted by the 

 living protoplasm of a vegetable cell to form its 

 investing membrane or cell-wall, passing through 

 the various ligneous, corky, and colloid changes, 

 new arrangement and union in cell- walls, &c. (see 

 CELL, LEAF, TISSUES, VEGETABLE PHYSIOLOGY, 

 WOOD). It is obtained pure by treating any 

 unaltered cellular tissue with alkalies and acids to 

 remove mineral matter and protoplasm, and suc- 

 cessive washings with water, alcohol, and ether to 

 remove soluble substances. Cotton-pith or vege- 

 table-ivory, although much contrasted in histologi- 

 cal properties, are alike remarkably pure cellulose ; 



in bast the proportion of associated mineral matte! 

 becomes much more considerable. Cellulose has the 

 chemical composition C 6 H 1(I O 5 , and spec. grav. 1 '52. 

 Among its familiar natural modifications gum is 

 an isomer, and starch-dextrin and grape-sugar are 

 all of similar ultimate composition, while its woody 

 and corky modifications ( lignin and suberin ) possess 

 an increasing proportion of carbon. Iodine alone 

 stains cellulose yellow or brown, but blue when 

 strong sulphuric acid has been previously added. 

 Strong hot sulphuric acid chars it, while brief im 

 mersion in the cold converts it into a tough and dense 

 modification, well known in parchment paper, and 

 prolonged treatment dissolves it altogether. Dex- 

 trin may thus be prepared and next transmuted, 

 by boiling the watery solution, into grape-sugar 

 (see DEXTRINE, GLUCOSE). By immersion in a 

 mixture of strong nitric and sulphuric acid we 

 obtain Gun-cotton (q.v.), while dilute nitric acid 

 or potash oxidises it into oxalic acid. Ammoniacal 

 oxide of copper dissolves it without change, as is 

 shown by its reprecipitation on dilution. By heat- 

 ing in closed vessels under pressure a dense coal- 

 like mass is formed, while in ordinary dry distilla- 

 tion, gas, tar, and acetic acid are given off, pro- 

 cesses which throw light on the formation of coal 

 in nature and on the chemistry of gas-making. In 

 natural decomposition cellulose turns yellow and 

 brown Avith gradual formation of humus. See 

 SOILS. 



Although so constant and characteristic a pro- 

 duct of vegetable life, the conditions and mode of 

 its formation are still very obscure. From that cell- 

 cycle or rhythm of change between the passive and 

 cellulose-walled state and an active and wall-less 

 one, which is so characteristic of the lowest forms 

 of life, and of which we find surviving traces 

 (e.g. the rejuvenescence of the pollen-grain) in the 

 reproductive processes of even the highest plants 

 (see CELL), it would appear that there is some 

 relation between this increased passivity and the 

 formation of cellulose. And in this way arises the 

 speculation that cellulose may be viewed essentially 

 as a (mechanically coherent and thus useful) 

 excretion, an incompletely utilised waste product 

 corresponding to the carbonic acid and water given 

 off by the completer respiratory oxidation and larger 

 evolution of energy of the active phase. Once 

 formed by the plant, it may be again absorbed, as 

 is well seen in the union of a row of cells into a con- 

 tinuous vessel, or in the consumption of endosperm 

 of a seed during germination. Many seeds, such 

 as vegetable-ivory or date, have a great pro- 

 portion of their reserve material in this form ; and 

 this must be digested into glucose by the growing 

 embryo, and again worked up into new protoplasm, 

 which deposits cellulose as before. Like the plant 

 itself, the similar digestive ferments of the animal 

 might thus be naturally expected to digest cellu- 

 lose ; and this is actually, to some extent, the case 

 with the delicate young cell-walls of many green 

 vegetables, as can be experimentally verified, even 

 in man ; while in herbivorous animals this power is 

 much developed, and the nutritive utilisation of 

 their fodder is thus increased to an important 

 extent. 



The cysts of amoabae and other protozoa appear 

 to be at least largely composed of cellulose, and the 

 external tunic of ascidians (see TUNICATA) is of 

 identical, or at least isomeric, composition. Cellu- 

 lose has been described as a pathological product, 

 even in brain-tissue; and Chitin (q.v.), a very char- 

 acteristic and in many respects comparable animal 

 product, has been sometimes viewed as cellulose in 

 association with a proteid substance. 



Celsius, ANDERS, the constructor of the centi- 

 grade thermometer, was born at Upsala in Sweden, 

 27th November 1701. He was the grandson of 



