N I T

NIT

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Nitrat of Potafh. It is alfo generated in feveralchemical precedes, and may be produced by thedirect union of its two conftituent parts, azot,and oxygen, in fufficient quantity to afford fatis-factory evidence of its chemical nature ; but forthe purpofes of the laboratory and manufacture,it is always prepared from nitre, by the additionof fome fubftance which has a ftronger affinitywith potaffi than the nitric acid has, affiftedby diftillation.

The moft antient way of procuring this acidand which is ftill praflifed in many countries(though now feldom in England) is by heatingftrongly a mixture of nitre and clay, or nitreand green vitriol, in earthen or iron retorts, andreceiving the acid vapour in proper veffels. Itwas foon found that alum and fome other vitri-olic falts anfwered the purpofe as well as thevitriol of iron, and laftly the great improvementwas made of employing the vitriolic acid alone,which is the method now univerfally adoptedin the laboratory, and chiefly in manufacture,in this country, where this acid is cheap.

The way of procuring the nitrous acid infmall quantities, is the following: take a plainglafs retort of any fize, put into it any quantityof dry purified nitre in powder (which need notbe very fine) dropping it through a paperfunnel, that none may lodge in the neck of theretort, and fill it not higher than at moft two-thirds of the capacity of the body of the veffel,when the nitre lies light and uncompreffed.Then pour in (through a glafs funnel, with aftem reaching nearly to the bottom) concentratedfulphuric acid equal to about half of the weightof the nitre, equally guarding againft any lodge-ment of it in the neck of the retort. Thenlute on a large tubulated glafs receiver, andcement the joinings with fat lute (the compofi-tion of which is defcribed under the articleCements). Thefe two are all the veffels abfolutelyrequired, but the tube of the receiver muft beonly loofely flopped, or (what is a better way)it ffiould dip into an empty bottle withoutluting the joinings. As however towards theend of the procefs much acid vapour paffes offwhich would be loft in the common way ofProceeding, and is partially condenfible by

rar ter ’i° ne ° r two bott i es of the Woulfe’s appa-t i us ’ half filled with water, may be added toTe . Cs ' Ver > and the abforption tubes carefully

be fuel h v! lat 1 ) one the acidulous water mayn bac h >nto the receiver, and mix with

1 cfld a , l ?‘ Tlle retort is then to be

dually * fand ' bath > atld the fire applied gra-

As foon as the nitre and fulphuric acid mix,faint orange-yellow fumes ariie, but very Ipa-ringly, till by the affiftance of heat the nitre iscompleatly difiolved in the acid. When thismixture begins to get hot the fumes increafe,and long wet ftreaks appear on the neck ofthe retort, which colled! and fall down in dropsin the receiver. The heat is now to be in-creafed till the mixture boils, and at this pointof gentle ebullition the materials are to be kept,during which the drops of acid fall in quickfucceffion into the receiver, and the receiveritfelf is lined with the fame ftreaks of acid drops.Towards the middle of the diftillation, whenboth retort and receiver are filled with the acidvapour, the colour is only a faint orange, fothat the materials within the retort can be feenwithout much difficulty by looking down (forthe hot fand ffiould be heaped up as high aspoffible, and above the level of the boiling fluid)and even if they cannot be conveniently feenthe procefs will be known to go on well by thegentle uniform hilling noife of the boilingmaterials, and the moderately rapid fall of con-denfed drops in the receiver, which laft ffiouldbe kept quite cold with wetted cloths on theoutfide if neceffary. During all this time little,if any, gas or vapour of any kind paffes beyondthe large receiver. At length the vapour in theretort becomes of a higher orange, which foon(and rather fuddenly) deepens into a very darkand nearlv opake, orange-red, fo that the materi-als can no longer be feen ; and a little afterwardsthefe begin to fwell confiderably, and to rifeflowly up to the neck of the retort, and if thiswas at firft more than half full, the hot half-fluidmatter is apt to flow over into the neck, andthence into the receiver, unlefs the heat of thefurnace be rapidly checked and the top of theretort cooled by removing the upper part of thefand. The diftillation is then to be continuedwith the heat kept up as high as poffible with-out boiling over, and the whole receiver nowbecomes darkened with red-orange fumes, whichfind their way on to the connected bottles, wherethey are chiefly condenfed in the water throughwhich they are forced. At the fame time how-ever a confiderable quantity of gas efcapes,which if examined, is found to be a mixture ofazot with a very large proportion of oxygen.When nothing further is given out and the heatis fufficient nearly to redden the bottom of theretort, the procefs is concluded.

The produffs of this diftillation are:—aquantity of ftrong heavy nitrous acid, of a brightyellow colour, emitting copious orange-redt 2