DE218570C - - Google Patents

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- JVl 218570 - CLASS 12 /. GROUP

LE NITROGENE S.A. in GENEVA, Switzerland.

from nitrogen oxides.

Patented in the German Empire on March 21, 1909.

If the nitrogen oxides, diluted with air, are left, as they are as waste products in some branches of the chemical industry or by oxidizing atmospheric nitrogen of the electric flame arc, absorb from caustic potash or caustic soda solutions, as is well known, a mixture of (potassium or sodium) nitrite and nitrate is formed, which remain in solution and which

ίο difficult due to fractional crystallization are to be separated because their solubility in water is considerable and approximately for both salts is the same size.

The object of the invention forming process aims, the bound in this way Nitrogen in the form of more easily separable and greater commercial value products to win. The following is the implementation of the method on the basis of an example. 20 game using an absorption solution containing lime or soda.

a) Absorption using milk of lime.

In these cases the process essentially consists in adding a mixture of potassium and sodium sulphate in such proportions to the aqueous solution which has been neutralized with the nitrogen oxides and which contains only the two salts Ca (NO ₃ I ₂ and Ca (NO ₂ I ₂₎ adds that the salt A ₂ 5 O _{4 is present} in an equivalent amount with the Ca (NO ₃ I ₂ , while the amount of the salt Na ₂ S O _{4 is} equivalent

• is valent to the salts Ca (NO _{2 I 2.} If these conditions are met, calcium sulfate in particular precipitates, which is separated by filtration or suction or the like. If necessary, the solution is concentrated a little to reduce the amount of liquid To make precipitation of the calcium sulfate as complete as possible.

After the separation of calcium sulphate, saltpeter K NO ₃ and sodium nitrite Na N0 separate from the solution by alternating concentration and letting it crystallize. ₂ , which are then cleaned using the usual methods.

It is understandable that the process can be carried out in such a way that the nitrogen oxides are either absorbed by milk of lime to which K ₂ S O ₄ and Na ₂ S O _{4 have been added} in proportions based on practical experience, or by a solution which is obtained by adding K ₂ SO _i and Na ₂ SO ₄ to lime milk beforehand in suitable proportions and separating the insoluble calcium sulfate which forms, whereupon the filtrate readily serves to absorb the nitrogen oxy de.

b) Absorption by alkaline solutions.

If the nitrogen oxides are to be absorbed by alkaline lyes, the usual sodium hydroxide solution is replaced by a solution containing sodium and potassium which contains the elements Na and K in the proportions in which nitrite and nitrate are formed by dissolving the nitrogen oxides. As is well known, results in ordinary

Temperature the dissolution of the oxides of nitrogen in aqueous media approximately one Equivalent of nitrous acid to one equivalent of nitric acid, while if the oxides of nitrogen are brought to higher temperatures', the amount of nitrite formed That of nitrate increases considerably in cost. But the same thing happens to a lesser extent, when the oxides of nitrogen with a large

ίο Excess air are diluted, especially when the content of nitrogen oxide is less than 6 percent. Up to 3 molecules of nitrite for 1 molecule of nitrate can be obtained under these different conditions. The solution containing soda and potash used for the above absorption is prepared from caustic soda and caustic potash or from the corresponding carbonates Na ₂ CO ₃ and K ₂ CO ₃ or from any other salts of sodium and potassium that can be decomposed by nitrous acid and dilute nitric acid .

In the case of embodiment a), instead of milk of lime, another one can be used to form a difficult one Use soluble salt capable compound, as one can of course use in place of the Sulphates of other salts of potassium and sodium can serve as far as they have the properties have to form a sparingly soluble salt with the lime or the other compound.

From the above it can be seen that the process can be carried out in several different ways can be carried out, the common feature of which is that one eventually always a solution is obtained from which the nitric acid as potassium nitrate when concentrated precipitates, while the nitrous acid remains in solution in the form of sodium nitrite and passes through subsequent narrowing can be obtained.

Claims (2)

Patent Claims: 1. Process for the simultaneous production of potassium nitrate and sodium nitrite by bringing together nitrogen oxides or their solutions with alkaline solutions, characterized by the Use of solutions from mixtures of sodium and sodium which can be decomposed by dilute nitrous acid and nitric acid Potassium compounds in proportions in which the dissolution The nitrogen oxides form nitrite and nitrate, using potassium nitrate and sodium nitrite from the solution obtained to be able to separate their different solubility. 2. Embodiment of the method according to claim 1, characterized in that the nitrogen oxides by such compounds (e.g. lime) and in the presence or with subsequent addition of such Salts of potassium and sodium (e.g. potassium and sodium sulfate) in the claim ι can absorb marked proportions that a reaction takes place with the formation of potassium nitrate and sodium nitrite.