NITBIO ACID 417 



absorbing oxygen. It is very soluble in water, alcohol, and the oils (fixed and vola- 

 tile) ; also in ether, -which has the power of extracting it completely from its aqueous 

 solution. 



It is very hygrometrical ; exposed to a moist atmosphere it rapidly absorbs water, 

 but loses it again in an atmosphere dried by potash. When thus hydrated it becomes 

 a solid crystalline mass if exposed to the cold of a mixture of ice and salt. When 

 anhydrous it does not become solid at 14 Fahr. It boils at 482 Fahr. and is at the 

 same time slightly decomposed ; but notwithstanding its high boiling-point, it may bo 

 easily distilled with the vapour of water without decomposition. 



The vapour of nicotine is so irritating, that we should experience a difficulty of 

 breathing in a room where a drop of that alkaloid had been volatilised. Its vapour 

 burns with a white smoky flame, depositing charcoal, like an essential oil. Nicotine 

 turns the plane of polarisation strongly to the left. From the volume of its vapour, 

 and from the quantity of sulphuric acid required to form with it a neutral salt, the 

 formula of nicotine would appear to be C 20 H M N S (C 10 H U T 2 ) ; but from some of its 

 combinations it would appear to be half of this, viz. C IO H 7 N. 



By the aid of heat nicotine dissolves sulphur, but not phosphorus. Nicotine unites 

 with acids, forming salts, which are very deliquescent, difficultly crystalli sable, in- 

 soluble in ether, except the acetate, and when pure possess no smell, but an acrid 

 tobacco taste. The double salts which nicotine forms crystallise much more easily. 



The aqueous solution of nicotine is colourless, transparent, and strongly alkaline ; 

 it forms a white precipitate in a solution of corrosive sublimate, also in a solution of 

 acetate of lead, and with both chlorides of tin. The precipitate which it forms with 

 solutions of the salts of zinc is soluble in an excess of nicotine. Salts of copper givo 

 with it, at first, blue precipitates, but these dissolve in excess of nicotine, forming a 

 deep blue solution, as they do when supersaturated with ammonia. Bichloride of 

 platinum yields with it a yellow granular precipitate. A solution of permanganate of 

 potash is immediately decolourised by a solution of nicotine. 



MTElIiO (Ital.). Nigellum. An art to which we owe the origin of engraving. It 

 consisted in drawing a design with a style upon gold and silver, and then cutting it 

 with a burin ; a black composition made by heating together copper, silver, lead, and 

 sulphur, which when cold was pounded, was then laid upon an engraved plate, a 

 little borax sprinkled over it, and placed over a charcoal fire, when the composition 

 dissolved and flowed into the lines of the design. When cold, the metal was scraped 

 and burnished, and the niello presented the effect of a drawing in black upon gold or 

 silver. The art was known to the ancients and practised during the middle ages ; 

 specimens, though rare are to be met with in museums. In the fifteenth century 

 these designs were frequently engraved with great delicacy, and the shadows hatched 

 with lines, precisely like a copper-plate engraving. The origin of taking paper im- 

 pressions from metal plates is ascribed to the practice of Maso Finiguerra, a Floren- 

 tine goldsmith, who, in the middle of the fifteenth century, was in the habit of taking 

 impressions of his incised work on cups and plaques in a viscid water-ink on paper, 

 for the pxtrpose of testing the state of his work. Such impressions of the early fathers 

 of copper-plate printing still exist, and are known also as niellos. See SULPHURS. 



NTOBIUHI. A metal discovered in 1801 by Hatchett in a mineral called columbite, 

 and hence it was named columbium. Eose rediscovered this metal in 1846, and gave 

 it the name it now bears. Niobium is a black powder ; specific gravity 6'27- See 

 Watts's ' Dictionary of Chemistry.' 



NITRATES OF AMMONIA, LEAD. POTASH, SILVER, SODA, 

 STRONTIA. The salts of nitric acid which are employed in the arts are described 

 under the heads of the metallic or earth constituent. 



NITRE. The common name for Nitrate of Potash. See POTASH, NITRATE OF. 

 NITRE, CUBIC. Nitrate of soda. See CUBIC NITEE and SODA, NITRATE OF, 

 Our Imports of cubic nitre have been as follow : 



1872 . 1873 



Tons Value Tons Value 



From Peru . . 1,365,195 1,045,383 2,176,239 1,604,040 



Bolivia . . 156,870 120,475 145,371 105,492 



Chili . . 55,966 42,451 85,260 57,173 



Other countries 16,166 12,122 537 426 



Total. . 1,594,197 1,220,411 2,407,407 1,767,131 



NITRIC ACID, Aquafortis (Acide nitrique, Fr. ; Salpetersaure, Ger.), exists, in 

 combination with the bases, potash, soda, lime, and magnesia, in both the mineral and 

 vegetable kingdoms. This acid is never found insulated. It was distilled from salt- 

 petre so long ago as thfi thirteenth century, by igniting that salt mixed with copperas 

 or clay, in a retort. Nitric acid is generated when a mixture of oxygen and nitrogen 



VOL. Ill, E E 



