N1TTUO ACID. 



hundred and seventy -sis degrees, dissolve 

 only 2.9. 



On being exposed to a gentle heat, 

 nitre fuses; and in this state being- pour- 

 ed into moulds, so as to form little round 

 cakes, or balls, it is called sal prunella, or 

 crystal mineral. This at least is the way 

 in which this salt is now usually prepar- 

 ed, conformably to the directions of Boer- 

 haave ; though in most dispensatories a 

 twenty -fourth part of sulphur was direct- 

 ed to be deflagrated on the nitre, before 

 it was poured" out. This salt should not 

 be left on the fire after it has entered in- 

 to fusion, otherwise it will be converted 

 into a nitrite of potash. If the heat be in- 

 creased to redness, the acid itself is de- 

 composed, and a considerable quantity of 

 tolerably pure oxygen gas is evolved, 

 succeeded by nitrogen. 



This salt powerfully promotes the com- 

 bustion of inflammable substances. Two 

 or three parts mixed with one of charcoal, 

 and set on fire, burn rapidly ; azote and 

 carbonic acid gas are given out, and a 

 small portion of the latter is retained by 

 the alkaline residuum, which was former- 

 ly called clyssus of nitre. Three parts 

 of nitre, two of subcarbonate of potash, 

 and one of sulphur, mixed together in a 

 warm mortar, form the fulminating pow- 

 der ; a small quantity of which, laid on a 

 fire shovel, and held over the fire till it 

 begins to melt, explodes with a loud sharp 

 noise. Mixed with sulphur and char- 

 coal, it forms gunpowder. See GUJTPOW* 



DEH. 



Three parts of nitre, one of sulphur, 

 and one of fine saw-dust, well mixed, 

 constitute what is called the powder of 

 fusion. If a bit of base copper be fold- 

 ed up and covered with this powder in 

 a walnut shell, and the powder be set on 

 fire with a lighted paper, it will deto- 

 nate rapidly, and fuse the metal into a 

 globule of sulphuret, without burning 

 the shell. 



If nitrate of potash be heated in a re- 

 tort, with half its weight of solid phospho- 

 ric or boracic acid, as soon as this acid 

 begins to enter into fusion, it combines 

 with the potash, and the nitric acid is ex- 

 pelled, accompanied with a small portion 

 of oxygen gas and nitric oxide. 



Silex, alumine, and barytes, decompose 

 this salt in a high temperature by uniting 

 with its base, as was observed when 

 speaking of aqua fortis. The alumine 

 will effect this even after it has been 

 made into pottery. 



The uses of nitre are various. Beside 

 those already indicated, it enters into the 



composition of fluxes, and is extensively 

 employed in metallurgy : it serves to pro- 

 mote the combustion of sulphur in fabri- 

 cating its acid ; it is r..- ed in the art of dy- 

 ing; it is added to common salt for pre- 

 serving meat, to which it gives a red hue ; 

 it is an ingredient in some fvigorih'c mix- 

 tures ; and it. is prescribed in medicine, 

 as cooling, febrifuge, :\ncl diuretic, and 

 some have recommended it mixed with 

 vinegar as a very powerful remedy for 

 the sea scurvy. 



Nitrate of socla, formerly called cubic 

 or quadrangular nitre, approaches in its 

 properties the nitrate of potash ; but dif- 

 fers from it in being somewhat more so- 

 luble in cold water, though less in hot, 

 which takes up little more, than its own 

 weight ; in being inclined to attract mois- 

 ture from the atmosphere ; and in crys- 

 tallizing in rhombs, orrhomboidal prisms. 

 It may be prepared by saturating soda with 

 the nitric acid, by precipitating nitric solu- 

 tions of the metals, or of the earths, except 

 barytes, by soda : by lixiviating and crys- 

 tallizing the residuum of common salt 

 distilled with three-fourths its weight 

 of nitric acid ; or by saturating the mo- 

 ther waters of nitre with soda instead of 

 potash. 



This salt has been considered as 

 useless; but professor Proust says, that 

 five parts of it, with one of charcoal 

 and one of sulphur, will burn three 

 times as loug as common powder, so as to 

 form an (Economical composition for fire- 

 works. 



Nitrate of strontian may be obtained in 

 the same manner as that of barytes, with 

 which it agrees in the shape of its crys- 

 tals, and most of its properties. It is 

 much more soluble, however, requiring 

 but four or five parts of water according 

 to Vauquelin, and only an equal weight 

 according to Mr, Henry. Boiling water 

 dissolves nearly twice as much as cold. 

 Applied to the wick of a candle, or add- 

 ed to burning alcohol, it gives a deep red 

 colour to the flame. On this account it 

 might be useful, perhaps, in the art of 

 pyrotechny. 



Nitrate of lime, the calcareous nitre of 

 older writers, abounds in the mortar of 

 old buildings, particularly those that have 

 been much exposed to animal effluvia, or 

 processes in which azote is set free. 

 Hence it abounds in nitre beds, as was 

 observed when treating of the nitrate of 

 potash. It may also be prepared artifi- 

 cially, by pouring dilute nitric acid on 

 carbonate of lime. If the solution bp 



