ACTIOY O F N I T R I C ACID ON METALS IK P R E S E S C E O F CATALYSTS BY C. C. PALIT AiYD K. R . D H S R
I n a previous paper' we have shown that if we start with dilute nitric acid and mercury a t the ordinary temperature, we always get crystals of mercurous nitrite after some hours. Moreover we have established that the maximum yield of mercurous nitrite is obtained when nitric acid of 2 6 7 concentration reacts with mercury at a temperature of 30'. TTe have also observed that ferric nitrate is a retarder in the action of nitric acid and mercury, though we have observed that ferrous sulphate accelerates the reaction between mercury and nitric acid. K e also have observed an interesting fact that. though the amount of mercury dissolved in dilute nitric acid in presence of ferric nitrate is less than in its absence, we have in all our experiments with nitric acid of 2 6 5 concentration, got much larger quantities of mercurous nitrite formed in presence of ferric nitrate than in its absence, This observation contradicts the previous observation of RAy2 who stated that in presence of ferric salts no crystal of mercurous nitrate is obtained in four hours. K e also have observed that in presence of mercurous nitrate, the yield of mercurous nitrite is much greater than in its absence. In this paper we have investigated the influence of various nitrates on the formation of mercurous nitrite by the action of nitric acid on mercury. The amount of mercury taken in each case was approximately 17.4 grms. in a
TABLE I Formation of crystals of mercurous nitrite in presence of various nitrate solutions of practically equivalent strength. Volume of HS03 = 2 j C.C.of 26%. Reaction = 24 hours. Temp. = 2 8 O C . S o . of experiment
1
2
3
Kame of nitrate solution added as catalyst
Blank hlercurous Titrate Ferric Nitrate
Amount of nitrate in grm. in I C . C . of the solution taken
Amount of mercurous nitrate formed in grm.
0 . j000
0.95 3 .oo
0,0142
2.95
Trace (one drop only) 4
5 6 7 8
9 IO
Do Do Manganous Sitrate Kickel Sitrate Cranium Sitrate Chromium Xitrate Cobalt Sitrate Copper Sitrate
' Z . anorg. Chem., 134, 191 (1924). * J. Chem. Soc., 99, 1012 (1911).
2.60
0.0340
2.93 2.03 1.42
0.0140
1.20
0 . 0 2j
1.18
0.OIji 0 . 0 2 jo
o 0.0164
I
.06
1126
C. C . PALIT A S D S .
R. DHAR
beaker and one cubic centimetre of approximately equivalent solutions of various nitrates ryas first added t o the mercury and then 2 5 C.C. of nitric acid of 26(% concentration xere added. The reaction was allowed to continue for 24 hours, the temperature being 28’. The results obtained are given in Table 1. The order of efficiency of the various nitrates is the following:llercurous nitrate > Ferric nitrate > Manganous nitrate > Sicltel nitrate > Uranium nitrate > Chromium nitrate > Cobalt nitrate > Copper nitrate. It seems probable that the decomposition of mercurous nitrite according to the equation Hg,(SO?j?%iIIg(SO?)? Hg is retarded by the presence of substances like ferric nitrate, nickelous nitrate, manganous nitrate etc., and hence in their presence the yield of mercurous nitrite is greater than in their absence. In a foregoing paper’, it has been proved that ferric salts can be reduced to the ferrous qtate by nitric ositle. Moreover ferric salts are also reduced by metallic mercury. Consequently the added ferric nitrate becomes ferrous nitrate which in its turn possibly reduces the mercuric nitrite into the mercurous state and thus the concentration of mercurous nitrite in the solution is increased. I t seems probable that manganous nitrate. nickelous nitrate, etc., are also capable of reducing the mercuric nitrite to the mercurous state and hence the yield of mercurous nitrite is greater in their presence than in their absence. In a previous paper?, the following remarks were made :“It seems certain that nitric acid is at first reduced to nitrous acid by the action of metals like bismuth, mercury. copper and silver and ferrous sulphate, sugar, and other substances”. In this paper, we have made further esperiments on the reaction of nitric acid on metals in order to find out whether nitrous acid is a product of the reaction between the different substances and nitric acid. The results are given in Table 11. In experiments xvith silver, lead and bismuth, crystals of nitrates were deposited after 48 hours. I n case of tellurium, a grey deposit of telluric acid was formed. In experiments with arsenic and antimony, a white deposit of As203and S b 2 0 awas formed. -4fter 3 hours each of theaboresolutions was tested colorimetrically for the amount of nitrous acid present. For this. equal volumes ( 2 c.c.j of each of the solutions were taken and then to each of them 2 C . C . of jcc solution of potassium iodide and I C.C. of starch solution were added to liberate iodine. The intensity of the colour developed was now compared and it was found that the amount of nitrous acid liberated was in the following order:Fe > Cu > Cd > d g > Zn > Co > S i > RIn > -41 > Pb > As > Sb > Bi > Te > Se.
+
Proc Aikad.TT-et .imsterdam, 2 8 , J. Phys. Chem., 29, 142 ( I 9 2 j ) .
jlj
(1919).
ACTION O F XITRIC A C I D O X XETALS TABLE
Volume of H S 0 3 added =;
a
" c
:
S a m e of eleiiicnts used i n t h e experiment
Z
~ ( a Silver j (b) do 2(a) Lead (h) do 3 (a) Cadmium (b) do 3(aj Bismuth (b) do j (a) Aluminium (I)! d0 6(a) Zinc (b) do ;(a) Cobalt (13) do 8(a) Sickel (b) do 9 (a) Manganese (b) do Io(a) Copper (b) do I I ( ~ )Iron (b) do 1 2 (a) Chromium (b) do 13 (a) Sulphur. (b) do I -1. (a) Selenium (b) do I j (a) Tellurium (b) do I 6 (a) Arsenic (b) do r.i(a) Antimony (b) do
S J y n g t h of nitric acid used in per cent. three hours
I3 26 I3 26 I3 26
I3 26 '3 26
I3 26 13 26 '3 26
13 26 I3 26 13 26
I3 26 I3 26
I3 26 I3 26 I3 26 I3 26
= 20 C.C.
S a t u r e of cheni,ical reartion during first hours of t h e reaction
Very slow Quick T7ery slight Slight 1-igorous d0 T-ery slon Slow S o action T-ery slight Quick T-igorous Quick TTgorous Quick T-igorous Quick d0 Slow Quick do TTgorous S o action do do do d0 T-ery slight d0 SlonT'ery slight Slow S o action Slow L
11 Temperature
Presence of nitrous acid during t h e first three
Slight Copious Slight d0 Copious d0 Slight d0 Si1 T-ery slight Copious do d0 do do d0 d0 d0 Copious d0 do do Kil d0 d0 d0 d0 T-ery slight d0 Slight d0 Copious Si1 Slight
1127
=
ordinary.
Presence of nitrous acid niter 2 4 hours of t h e reaction
Si1 d0 d0 d0 do d0 d0 d0 Slight Copious Si1 d0 d0 do do d0 do do Slight d0 Fair d0 Si1 d0 d0 d0 d0 do TTeryslight Slight d0 Fair Slight T-ery slight
Amount of t h e element dissolved in z i hours
Complete do Slight d0 Complete d0 Slight d0 Slight Fair Complete d0 do d0 d0 d0 do d0 do d0 do d0 Si1 d0 d0 d0 do Very slight Slight Fair do d0 Slight d0
In case of sulphur and chromium, no colour developed showing the absence of nitrous acid. Consequently the above experiments conclusively prove that in all cases nitrous acid is the first product between the reaction of the elements and nitric acid and the above esperiments confirm our view that nitrous acid is the primary product of the reaction between nitric acid and the metals.
C . C . PALIT AND N. R. D H h R
1128
In several papers1 published from these laboratories, lve have shown that slow oxidation of substances like sodium sulphite, ferrous hydroxide, phosphorus etc., is markedly retarded by the presence of reducing agents like sugar,2 sodium arsenite, and organic substances. Moreover in a previous paper it has been shown that substances like tartaric acid, urea, ether, acetic anhydride, benzoic anhydride. etc., retard the action of nitric acid on copper whilst substances like strychnine sulphate, phthalic anhydride, arsenious oxide, carbon tetrachloride, etc., accelerate the reaction between nitric acid and copper. TTe have made further experiments on the action of nitric acid on copper and mercury in presence of reducing agents and the experimental results are given in Table 111.
TABLE I11 T'olume of H S 0 3 = S o . n!
experiment
Substance used as reducing
agent
2 0 C.C.
of 26:;. Tolume of reducing agent Reaction = 4 hrs.
Strength of reducing agent
Total
volumr of the solution In c . r
I
Blank
___
2 j
= 5 C.C.
h n i o u n t of ropper Amount of Amount dissolved i n grin. a t inercury of niercurn temperature of dissolx.ed i n ous n i t r a t e 240c ?o"C g r m a t 20°C formed in 2oT
o 6464
o 3146
4 6924
o
j 2
Molar 2 Tartaric Acid solution 4 6880 o 42 do o 3388 o 2324 do o 2804 o 2 7 1 8 3 Citric Acid do 4 1858 o 43 do 0 2402 4 3510 0.48 4 Glucose do 0 1168 o 2 2 j 0 o 1486 5 Formic Acid do do 4 8640 o 46 do do o 1646 o 0892 6 Cane Sugar 4 5118 o 37 ; Glycerine do do o 0876 0 0816 4 2 0 2 4 o 28 8 Oxalic Acid do do o ooj8 o 0028 o 9 j 8 0 o 00 In each of the above experiments the volume of nitric acid used was 20 C.C. of 26% concentration and the volume of the reducing agent added was 5 C.C. the total volume being 25 C.C. I n the blank experiment only 5 C.C. of distilled water were added to make the total volume 2 j C.C. The duration of reaction was 4 hours. It will be seen from Table I11 that all the reducing agents used in our experiments, namely tartaric acid, citric acid, formic acid, oxalic acid, glycerine, glucose and cane sugar, act as marked retarders in the reaction between nitric acid on copper or mercury and the order of the retarding action is the following :I n the case of copper a t 24OC, tartaric acid > citric acid > glucose > formic acid > cane sugar > glycerine > oxalic acid and at 2ooC, citric acid > tartaric acid > formic acid > glucose > cane sugar > glycerine > oxalic acid. In the case of mercury at 2 o ° C , formic acid > tartaric acid > cane sugar > glucose > glycerine > citric acid > oxalic acid. J. Chem. SOC., 111, 707 (1917); Proc..ikad. Wet. =Imsterdam, 23, 1074 (1921);Trans. Faraday. SOC., 14, I , 17 (1922). * Dhar: loc. cit.
1129
ACTION O F X I T R I C A C I D OK METALS
In the reaction liet,ween nitric acid and mercury, formic acid acts as an accelerator. I n the case of oxalic acid, precipitates of cupric oxalate and mercurous oxalate are formed which cover the metals and protect them from further action. That is n h y oxalic acid is such a great, retarder. The yield of mercurous nitrite was very small in these cases, though the amount of mercury dissolved was fairly large in several cases. It’ seems probahle that the organic substances like tartaric acid. citric acid, glycerine, etc., combine and form complex ions with mercurous nitrite and mercuric nitrite. Many complex ions containing mercury are well known. The retarding action of these substances is prohably associated n i t h their reaction on the active substance, viz. nitrous acid. The nitrous acid which is formed by the action of copper or mercury on nitric acid is possibly partially destroyed hy its reaction on the reducing agents like tartaric acid, citric acid, glycerol etc. It is ne11 known that sulphur compounds retard the slow oxidation of phosphorus. Recently 1Ioureu anti Dufraisse‘ have shon-n that many sulphur compounds retard several oxidation reactions. S o w in order to find out whether the sulphur conipounds retard the oxidation of copper and mercury by nit,ric acid, we have investigated the influence of various sulphur conipounds on this reaction. The experimental results are given in Table IT-.
TABLEIT7 2 0 c.c.1 i) volume of sulphur compd of 2 6 5 ii) ,, ,,
i ) volume of HSOa = ij) ” )’ = 1 5 C.C.! of So., of ex- S a m e oi Sulphur pertinent coiiipound used
”
1 7 .
c.c.1 ?.e.,(
Total volume = 2 j C.C. Reaction = 4 hours.
Strength oi sulphur roiiipound
.kniount oi copper .kiuount of mercury .\mount of mercurd k s o l v e d in grill. i n dissolved in g r i n i n ou? nitrite ioriiicd prewnce r i f sulphur presenw of sulphur i n g r m . i n pre*enr,r coiiipound t a k e n compound t a k e n of sulphur c o m pound t,?1ien.
jr,e
Blank Sodium-P-napht halene sulphonate Sulphonal Sodium-an thraquinone sulphonate Sodium-benzene sulphonate Thio-urea Sodium-@-naphthalene sulphonate Sulphanilic Acid
= 5 = IO
I O C . ~ .
5c.c.
10c.c.
10c.r.
ioc.
__ 0.64300.0908
0.12
1.05
0.00 0.00
6.0616 3.6834 0.6948 0.0844 3.4578 0.0994
0.09
do do
0.6894 0 . 0 7 2 2 5.3394 3.1960 do do 0.6880 0.0852 6.4320 0.8694 do do
do
0.6620 0 . 0 7 7 2
do do
0.6570 0.0476 0.0036 0.0012 0.00 do 0.59j4 0 . 0 7 1 2 6.70123.5060 0.24 do
do
0.01960.0136 3,1306o.ooj6
6 . j 5 3 4 3.3126
0.25
0.00
do
do
In each of the above experiments, 2 0 C . C . of nitric acid of 2 6 5 concentration and j C.C.of the solution of the sulphur compound were used in one set ‘Compt. rend., 178,824. 1397, 1862; 179, 237 (1924).
1130
C . C . P.iLIT .AND S . R . D H A i R
antl I ; C.C. of nitric acid of the same concentration and I O C.C. of the sulphur compound were used in the other set so that the total volume in each case being z j C . C . In the blank experiment, only 5 C.C. or I O c.c. of distilled water vere added t o 2 0 C . C . or 1 5 C . C . of nitric acid t o malie the total volume 2 j C.C. The duration of reaction 11-as 3 hours at' Z ~ ' C ( .
The experimental results on the reaction of nitric acid on copper show that small quantities of sodiuni-~-naphthalene sulphonate, sulphonal, sodiumanthraquinone sulphonate. sodium benzene sulphonate antl thiourea appreciably accelerate the reaction n-hilst sotliiim-oc-n:~phthalene sulphonate is a n-eak and snlphanilic acid a powerfiil retarder. TT-hen the concentration of the sulphur compounds is tlonliled, all of them are retarders. K i t h mercury and nitric acid. small quantities of sotliuni-oc-naphthalene sulphonate, sodiumbenzene sulphonate. antl sodiun~-anthraquinonesulphonate are accelerators whilst sulphonal, sotliuIn-i3-naphthalene sulphonate. sulphanilic acid antl thiourea are retarders. K h e n the quantity of sulphur compountk is doubletl. d l of them in this case as well are retarder$. The yield of nierctirous nitrite liy the action of merciiry and nitric acitl in presence of these sulphur conipounds is in many c : ~ . :nil and in others very small. I t seems very prohable that this is due t o the fact that complex sulistances are formetl lietween mercuric and nierciiroiis ions ant1 the sulphur coinpountls;. It is n-ell l a o w n that sulphnr compounds have a great affinity for mercury compounds antl many stable complex ions containing sulphur nncl mcrcury are 1inon.n. The retarding effect of these sulphur compountls, when stronger solutions are used, is most probably caused hy their :iction on the active substance namely the nitrous acid which is partly destroyed hy its reaction on the sulphur compounds. S o w some of the sulphur compounds in small quantities act as a feeble accelerator in the action of copper or merciir?- on nitric acid. I t is quite prohahle that small quantities of these sulistances would act on the nitric acid and generate nitrous acid which would accelerate the chemical change. Consequently it, is prohahle that two opposing reactions are taking place in the solution, viz. ( I the forination of nitrous acid 11)- tlie reducing action of the sulphur compounds on nitric acid and ( 2 ) the removal of nitrous acid by their reaction on t,he sulphur compountls. S o w at such concentrat,ions of the sulphur compormtls, when the first action predomiiiates over the second, n-e are likely t o get acceleration whilst when the second reaction counter-balances the first we get retardation. There is another factor which might lead to retardation antl that is the adsorption of the sulphur compounds on the surface of the metals. C'opper antl mercury have a great, affinity for sulphur compounds and it is prohable that some of the sulphur compounds n-ould be adsorbed antl be deposited on the surface of the metals antl would partilly prevent or retard the react,ion between the metals and nitric acid. Moreover the amount of adsorption will be greater, the greater the concentration of the sulphur compounds.
1131
A C T I O S O F S I T R I C A C I D O S METALS
Conroy' found that arsenious acid retards the action of iron and hydrochloric acid but n.e have found that the action of copper and nitric acid is accelerated by arsenious acid. The accelerating effect is caused by the reduction of nitric acid t o nitrous acid by the pre>ence of arsenious acid. I n this investigation n-e have studied the influence of ten alkaloids on the reaction lietn een nitric acid antl copper or mercury. The experimental results are given in Table I-. TaBLE
2 volume of HSO? = ii) *' =
2 0 C.C. 1 . ; C.C.
i) voliiine of allialoitl ii) ''
(of 26';
Total volume
J-
= 2.j C . C .
Reaction
= 1, hours
i o i c
i c c
j i c
7
3 4 7
6 /
8 9 IO
Blank Sarcoline Strychnine Quinidine Sulphate Quinine Sulphate Cinchonine 3Iorphine Hytlrochlor. Brucine Caffeine Cocaine Hydrochlor.
=
5 c.c.1
= IO C . C .
I O C !
(Of;'1
j ! C
ioic
4.6976 2.4190 0.48 Si1 6.07142 . j i 4 4 Si1 do 0 . 6 2 5 2 0.2172 6.0020 2 . ~ 2 0 0 do do 0.61560.1216 j.6986 1.9698 0.46 do 0.6070 0.1114 6.06441.9014 0.07 do 0.6050 0.0664 ;.8850 2.4174 0.1; do 0..;7040.1181, i.8356 2.7612 s i 1 do o..i682 O.III.; -;.TO562 . 9 7 2 0 0.05 do 6.7682 2.3772 0 . 1 0 do 0 . ~ i ~ 90.0.;68 2 0.2366 0.0616 .i.8698 O.O-i;8 Si1 do 0.;280 O . I O T 8
0.6524
0.1172
In case of the ahove experiments. 2 0 C.C. of nitric acid of 2 6 r 7 concentration antl 5 C . C . cf the solution of allialoid were used in one set and 15 C . C . of nitric acid of the same concentration and IO c.c. of the solution of the allialoid n-ere used in the other set, $ 0 that the total volume in each case k i n g 2 5 C . C . I n making the solutions of the alkaloids, each of thein was tlissols.etl in 5 C . C . of nitric acid of 2 0 5 concentration antl the solution was made up t o 100c.c. ;Ilso ;. c.c. of the same nitric acid of 2 0 5 n-ere made up t o 100C . C . with clistilled water antl this solution n-as iiPet1 in the case of the hlanli experiment,. I n the l~lanliexperiment only ;. c.c. or I O C . C . of the aliove dilute nitric acid were added t o 2 0 c.c. or 1 5 c.c. of nitric acid of 2 6 ( ; concentration t o make the total volume 2 5 c.c. The duration of reaction was 1, hours a t 2 IO('. From the above experimental results it will be observed that in the reaction lietn-een nitric acid antl copper. narcotine. strychnine, quinidine sulphate, quinine sulphate. cinchonine, morphine hytlrochloritle. lirucine, antl caffeine act as feeble accelerators whilst cocaine hytlrochloritle is the only retarder. when small quantities of these substances are added. \\-hen the concentration of these alkaloids is tlouhlecl~cinchonine, cocaine hydrochloride, J. SOC.Chem. Intl., 20, 316 (1901).
C . C . P l L I T A N D S . R . DHAR
1132
and caffeine are retarders whilst the others are accelerators. In presence of small quantities of all the ahove alkaloids, the reaction between mercury and nitric acid is accelerated, whilst the concentration of the alkaloids is doubled, cinchonine, caffeine, quinidine sulphate and quinine sulphate act as feeble retarders whilst cocaine hydrochloride acts as a marked retarder, the other alkaloids remaining accelerators. In the case of cocaine hydrochloride copious precipitate was obtained due to the reaction hetween cocaine and mercuric and mercurous salts in the qolution. The explanation of the accelerating antl the retarding effects of these alkaloids if probably the same as that advanced in the ca5e of sulphur compountls. In a recent paper, Rane and N a t a Prasad' have shown that alkaloids retard the reaction hetn-een iron and hydrochloric acid. K e have also investipuLet1 the influence of sunlight on the reaction lietween nitric acid antl coppel' antl mercury. In a preTious paper? it has heen shon n that most chemical reactions are accelerated hy sunlight and the (lata in Table T71 show that the action of nitric acid on copper or mercury is highly accelerated by sunlight :-
TABIL1-1 i) Temperature inside the room ii) " in wnlight
Reaction = 4 hours ~ I O CStrength of HS03 = 26';
= 2o°C
=
I
I
I
1 1
I
copper Mercury
nitrite formed in grni.
I
Substance used in t h e experiment
2
.\mount of inereurnus
I
20 5 d o , do
o 3146 o 6802 1 o 8158 -- -- 1 d o ' 4 6924 1 6 5 2 4 2 7 3674 o j z 1 o 6; 25
~
~
1
1
__
0.63
Summary I. hIaximum yield of mercurous nitrite is obtained with nitric acid of ~6~~concentration at a temperature of 3ooc. K h e n approximately equivalent solutions of Yarious nitrates are added 2. in the reaction between nitric acid and mercury, the amount of mercurous nitrite is greatly influenced by their presence. The order of their efficiency is the following:Mercurous nitrate > ferric nitrate > manganous nitrate > nickel nitrate > uranium nitrate > chromium nitrate > cobalt nitrate > copper nitrate.
J. P h y s Chem. 2 9 , 249 i 1 9 2 j ) . Proc. .Ikad. n - e t . ;Imsterdam, 24, 1324 (1916)
S C T I O N O F N I T R I C ACID ON 31EThLS
1133
3 . K h e n nitric acid reacts with an element, nitrous acid is the primary product of the reaction. S o nitrous acid is formed when no reaction takes place between the element and the nitric acid. 4. In the reaction between nitric acid and copper, reducing agents like tartaric acid. citric acid, formic acid, osalic acid. glycerine, glucose, or cane sugar act a3 marked retarders whilst in the reaction between nitric acid and mercury. all the above reducing agents except formic acid act as marked retarders, formic acid being in this case an accelerator. -Us0 the yield of inerciirous nitrite in these cases is very small although the amount of mercury dissolved is fairly large in several cases. 5. Organic sulphur compounds in small concentration act in some case'. as accelerators and in others as retarders in the reaction bemeen nitric acid and copper or mercury, whilst in greater concentration. all of them act as retarders. Similar results are obtained when several alkaloids are used instead of the organic sulphur compounds. 6. The reaction between nitric acid and copper or mercury is greatly accelerated in sunlight. Clieiiiical L n b o m t o q , Allahabad 17nizers/tg, d / l a ii a bad. V a i c l i 30, 19516
