TAR, COAL 



969 



brought from North America, and he called it, on that account, Columbium. Ekeberg 

 discovered it in 1803 in the Swedish minerals, and, considering it a new metal, he called 

 it Tantalum. Dr. Wollaston, in 1809, sought to show that Hatchett's columbium and 

 Ekeberg's tantalum were one and the same substance ; but H. Rose afterwards proved 

 that they were distinct, and gave the name of Niobium to the former columbium. 



Tantalum has not yet been applied to any commercial purpose. 



TAP-CINDER. Puddling-furnace slag. This is a basic silicate of iron. Its 

 general composition may be seen from the following analysis of tap-cinder from a 

 Staffordshire furnace, by Dr. Percy : silica 23'86, protoxide of iron 39'83, peroxide of 

 iron 23'75, protoxide of manganese 6'17, alumina 0'91, lime 0'28, sulphide of iron 

 - 62, phosphoric acid G - 42. See IKON and SLAG. 



TAP-HOLE. The hole in a puddling furnace, through which the slag flows out. 



TAPESTRY is an ornamental figured textile fabric of worsted or silk, for lining 

 the walls of apartments ; of which the most famous is that of the Gobelins Eoyal 

 Manufactory, near Paris. See CABPETS, LACE, TEXTILE FABRICS, and WEAVING. 



TAPIOCA. (Manioc and Cipipa, Fr. ; Weisse Sago, Ger.) Tapioca is cassava- 

 meal, which, while moist or damp, has been heated, for the purpose of drying it, on 

 hot plates. By this treatment the starch-grains swell, many of them burst, and the 

 whole agglomerates in small irregular masses or lumps. The drying to which it is 

 subjected renders it difficult of solution. In boiling water it swells up, and forms 

 a viscous jelly-like mass. See STABCH. 



TAO.TTA NUT. The vegetable ivory of commerce. See IVORY, VEGETABLE. 



TAR, COAL This substance, when properly distilled, is capable of yielding 

 naphtha, a fixed oil, and pitch, the two former of which are vastly more valuable than 

 tar. The relative proportion of these products is, however, very variable, according 

 to the kind and quality of the tar employed. Thus tar from the condenser is more 

 valuable for its products than the tar of the same coal taken from the hydraulic main, 

 and again cannel coal-tar is always superior to common coal-tar. In general we may 

 estimate the available amount of the volatile and fixed matters of coal somewhat in 

 the following order : 



Naphtha Dead oil Pitch 



Common coal-tar 3 62 35 



Ordinary cannel tar 9 60 31 



Boghead cannel tar 15 67 18 



Of these the naphtha is in large demand for the solution of caoutchouc, the lighting 



