PREPARATION OF NITRIC OXIDE: SOME LABORATORY METHODS M. G. SURYARAMAN and ARCOT VISWANATHAN Madras Christian College, Tambaram, South India
Nmw oxide prepared in the laboratory from solutions
Sodium cobaltinitrite, in the reactions tried, appeared to behave as a mixture of sodium nitrite and cobaltic nitrite and evolved nitric oKide. The results of small-scale experiments conducted with the solids showed that the equations cited could represent the course of the main reactions under dry and moist conditions. The results stated in the table were obtained in separate experiments. The gas was collected over water after rejecting the first portions. The gas volumes stated are approximate a t room temperature (2%31°C.) and pressure (about 760 mm.). It was found that the water of hydration of the ferrous salt was sufficientfor the reactions, in Experiments 1 and 4a, b, c, d, to proceed a t room temperature, although in Experiment l the last portion of the gas could be expelled only by heat. Higher temperatures were necessary when the water content present as water of crystallization was diminished or was absent from the reacting mixture (Experiments 2, 3a, 3b, 5, 6b). Some nitrogen was present as contamination in every preparation but no nitrous oxide could be readily detected. The latter gas could therefore be present only in such quantities, if formed a t all, as should have been taken up by the water. The use of hydrated or dehydrated salts made no difference in the purity of the gas obtained from the same reaction. The presence of the alkali halides in the mixture had an indifferent effect on the purity of the gas (Experiments 4a, 4b), except in Experiments 4c and 4d where the nitrogen contamination was slightly diminished (L. Moser and L. W. Winkler) (11, 23). In the experiments in which hydrated copper sulfate was employed the volume of nitric oxide obtained a t the boiling point of water was considerably less than the expected volume and (C. G. Macarthur) (26). Recrystallized, fused, and powdered sodium nitrite (14) and sodium cobaltinitrite (NaaCo(NOl)s~1/3H20. The ferrous nitrite decomposed spontaneously at room B.D.H.) were used. Dehydrated ferrous sulfate was temperature evolving nitric oxide. Cuprous chloride prepared from the purest samples of ferrous sulfate crystals available (FeSO4.7Hz0) according to the reacted with sodium nitrite as follows: method of J. A. Hedvall and J. Heuberger (6) with a s l i ~ h modification. t Merck's ~artiallvdehvdrated fer"Y2\i."1,2 T ro;s sulfate which is a pale-yellow powier (labeled The unstable cuprous nitrite decomposed and furnished "dry") used in Experiment 2 was found on analysis to the nitric oxide. Cupric nitrite, in solution, (W. Hampe contain some moisture and about 75 per cent of the ferer crvstals (CUSOA.~H.O\ were and P. C. Ray) (5, 16) evolved nitric oxide by au- rous salt. C o ~ ~sulfate ~. - ~ - , toxidation and reduction as follows: dehydrated aceordiua to themethod of T. W. Richards (17j. Dry cuprous chloride was prepared from copper sulfate by the method due to M. Rosenfeld and F.
of alkali nitrate or nitrite by the various reactions usually employed (1, 2, 4, 7, 9, 13, 21) is found to be sufficiently pure for classroom purposes, although the nitrogen impurity found in the gas varies from 1 to 30 per cent depending on the reaction selected (10,ll). A few dry methods of producing the gas with a high or low nitrogen contamination have been reported. The reactions so far chosen were: (a) heating a mixture of potassium nitrate and potassium carbonate with oxides like chromium sesquioxide, etc. ( 2 ) (6) heating boron nitride with oxides of iron, copper, etc. ( 9 0 2 and (c) thermal decomposition of diphenyl-nitroso-amine (8). This compound evolved nitric oxide 99.7 per cent pure (8). Some laboratory methods of generating the gas from sodium nitrite and sodium cobaltinitrite by reactions in the solid phase are described in this paper. These two compounds were found capable of evolving nitric oxide smoothly, when allowed to react with ferrous sulfate, cuprous chloride, and copper sulfate. Purified compounds were employed and experimental conditions were varied in several attempts a t reducing the contaminations in the gas evolved. Compounds like potassium cyanide, potassium ferrocyanide, and sodium hypophosphite were not used with the nitrite, as such mixtures are known to be explosive when heated. Potassium nitrate when substituted for sodium nitrite in the reactions tried, was found unsuitable as a source for nitric oxide, as it produced also considerable quantities of nitrogen and nitrous oxide. The action of ferrous sulfate solution on barium nitrite solution was studied quantitatively by P. Piccni and F. M. Zuco (15), who proposed for the reaction the equation:
l " " "
*I."
~~
~
~
NOVEMBER, 1949
Wohler (18, 65). Nitric oxide was analyzed over alkaline sulfite (Diver's Reagent) (3) prepared according to a modification of L. Moser and R. Herzner (1%)(15 per cent sodium sulfite and 1 per cent sodium hydroxide). The unabsorbed residue left was taken as nitrogen. The apparatus for the experiments consisted of a round-bottom flask fitted with a delivery tube. The quantities of the salts taken in the experiments were according to the proportions shown in the equations stated, keeping the ferrous or the copper compound in slight excess over the nitrite component. In experiments in which the hydrated ferrous salt was used the reactants were separately ground to fine powder, added in alternate layers to the flask, and mixed quickly by shaking. The reaction commenced a t once, followed by frothing of the contents (Experiments 1 and 4a, h, c, d). In every other experiment the salts were ground together intimately in a mortar before heing put into the flask. In each preparation, under the conditions mentioned in the table, there was a steady evolution of the gas which was washed through dilute alkali to remove the red fumes initially present and collected over water in a series of gas jars or in a gas holder.
While some of the experiments in the list could be selected for the classroom preparation of nitric oxide, the first one is found suitable for a quick preparation of several liters of the gas for the lecture table. It is not necessary to use purified or dehydrated salts. The decomposition of the ferrous nitrite in the experiment is accelerated by the addition of water or retarded by chilling the flask to 0°C. These effects are capable of heing demonstrated as individual experiments. Cobalt sulfate reacted with the nitrite salt like copper sulfate (Experiments 7d, 8a, 8b) (W. Hampe 5) and yielded nitric oxide distinctly less than the expected volume (Experiments 6a, 7c, 7d, 8a). This could be explained by the fact that a part of the nitrite was converted into a basic nitrite of copper or cobalt and remained unchanged with the residue (W. Hampe 5: 67). Oxalates of lead and cobalt heated with sodium nitrite evolved nitric oxide and carbon dioxide: PbC,O,
+ 2NaN01 = PbCOa + NanCOa + 2NO PbC08 = PbO + CO2
The gas was collected after removing the carbon dioxide by sodium hydroxide solution. An excess of the nitrite
Size of the roun& bottom.
Ezpt. No. 1
Weights - o .f the solids i n the r e a c h mulure
52 g. FeS0,.7H20 and 25 g. NaNOl
fE&
ml. 500
Heatino sourFirst a t room temperature Later in hat water Hot water or burner
Burner Burner
and 8.5 g. KI, and 4
CN~NO~
11 g. Cu2Ch and 7 g. NaN02 39 g. CuS04.5H20and 20 g. NaNOn
,'--'-
10 g. CuS01.5H20 and 5 g. NaaCo(NO%)*. l/~H20 8g. CoSO4.7H2Oand 5 g. Na,Co(NOn)s'/a10 7.5 g. PbCzO~and 4 g. NalCo(NOl)o-
'/A0
4.5 g. CoC20,.2H20 and 4 g. Na,Co(NO,)$.'/,H,O 11 g. CaS0,.7H10. and 5 g. N ~ N O I 6 g. CoSO, and 5 g. NaN02 7.5 g. PbCnO, and 4 g. NaNOn 4.5 e. CoCZ0..2HaO and 4 n. NaN02.
A?. prozzmale Purity of nitric volume oxide of the Nitm- Nitric gas gen oxide collected, perperColw o f the residue liters eentooe centaoe Brown Brown
Room temperature
Brown Residue brown, some iodine vapors evolved Brown
Raom temperature
Brown
Room temperature
Brown
Room temperature
Residue brown, some iodine vapors evolved Blaok Bluish green
Burner Hot water (90100°C.) Burner Water bath (100'C.)
Black Brown
Burner
Black
Water bath (100°C.)
Grayish blue
Water bath (100'C.)
Yellowish pink
Burner
Black
Burner
Blaok
Water bath (100 'C.) Burner Burner Burner
Pink Black Yellow to red Black
5
1.8
98.2
JOURNAL OF CHEMICAL EDUCATION
had to be qsed to consume the oxalate completely, as LITERATURE CITED otherwise any unchanged oxalate left over a t the end would decompose on heating and contaminate the gas (1) C m s , L., Liebigs Ann. Chem., 94, 138 (1855). with carbon monoxide. No carbonaceous matter (2) DEVENTER,C. M., Ber., 26, 589 (1893). was seen to separate in the oxalate reactions. (3) DIVERS,E., PTOC.Chem. Soc., 221 (1898); J. Chem. Soe., 82 -- llXQ!?\~ \----,. Oxalates of lead and cobalt (PbCeOd (28) B.D.H. and (4) GAYLUSSAC,Ann. ehim. et phys., 23,203 (1847). CoC20~2Hz0Merck) were used. Cobalt sulfate (5) HAMPE,W., Liebigs Ann. Chem., 125, 345 (1863). (COSOC~HZO) was dehydrated (Experiment 8b) follow- (6) HEDVALL,J. A,, AND J. HEWERGER,Zeit. Anorg. Chern., ing the method of T. E. Thorpe and J. I. Watts (29). 128, 2 (1923). (7) KXMMERER, H., Ber., 18,3064 (1885). About a liter of the gas evolved from each of the (8) M ~ Q U E Y R O AND L FLOEENTIN, Bull. Soc. Chim., 11, 805 nitrite-oxalate reactions (Experiments 7e, 7f, 9a, 9b) 11912). and washed through dilute sodium hydroxide was con(9) M~LLON; N. A. E., Compt. rend., 14, 904 (1842). 6ned over Diver's Reagent to remove the nitric oxide (10) MORRIS,V. N., J. Am. Chem. Soc., 49, 982 (1927). completely. The residual gas was mixed with excess (11) MOSER,L., Zeit. Anal. Chem., 50, 403 (1911). ibid., 64, 87 (1924). of air and sparked over mercury in a sparking tube. (12) MOSEB,L., AND R. HERZNER, (13) NOYES,W. A,, J. Am. Chem. Soc., 47, 2170 (1925). A clear solution of baryta introduced into the gas (14) PARTINGTON, J. A,, "Textbook of Inorganic Chemistry for residue failed to give a precipitate of barium carbonate, University Students," 5th ed., Macmillan & Ca., New showing that the gas contained no CO as impurity. York. 1937...o. 583. PICCNI,'P.,AND F. M. ZUCO, G Z Zehim. . ital., 15,475 (1885). It was found in trial experiments that sodium nitrite RAY, P. C., J. Chem. Sac., 91, 1405 (1907). when reduced by heating with cuprous oxide, cuprous RICHARDS, T. W., Proe. Am. Acad., 26, 240 (1891). iodide, calcium sulfite, chromium sesquioxide (CrzOJ), ROSENFELD, M., Ber., 12, 954 (1879). antimony trioxide, and oxalates of nickel, calcium, and SBORGI, U., AND E. GAGLIARDO, Ann. Chim. Applicala, 14, 113 (1924). sodium gave nitric oxide contaminated with free nitroSBDRGI,U., AND A. G. NASINI,Gazz. chim. ilal., 52, 369 gen ranging from 4 to 25 per cent. A mixture of sodium 11922). nitrite with sodium phosphite or sodium formate was TALE; J., Liebigs Ann. Chem., 253, 246 (1889). found to deflagrate violently when heated. Potassium WAGNER,A,, Zeit. Anal. Chem., 18, 552 (1879). nitrate, when reduced by beating with the oxalates, WINKLEE,L. W., Ber., 34, 1409 (1901). WOHLER, F., Liebigs Ann. Chem., 105, 259 (1858). gave nitric oxide with 20 per cent nitrogen impurity. WOHLER, F., ibid., 130, 373 (1864). In Experiments 3a, 3b, 5, 6b, 7b, 7e, 7f, 8b, 9a, 9b a M A ~ A R T HC.~ R G., , J. Phys. Chem., 20,545 (1916). pyrex tube could be conveniently substituted for the MELWR,J . W., "A Comprehensive Treatise on Inorganic round-bottom flask, and the evolution of nitric oxide Chemistry," Longmans, Green & Co., New York, 1928, V01.8, p. 479. could also be regulated by the burner, while in ExperiSEIDELL, A., "Solubilities of Inorganic and Metal Organic ment 2, a 40-watt electric bulb held inside an asbestos Compounds," 3rd ed., D . Van Nostrand Co., New York, cylinder would serve the purpose as a heater. 1940, p. 1383. The experiments listed in the table, produce nearly THORPE, T. E., AND J . I. WATTS,J. C h a . Soe., 37, 112 pure nitric oxide (1.2-2.5 per cent N2 impurity). (1880). ~~~~
ICormn's KOTE: Tllr euprrimtwts involving cobalt were done subsequmrly to the rompletim of tlw original paper and h a w hrvn adrlcd as additional material.
