2--The concentration oi nitric acid must not exceed a certain limit. A favorable range lies apparently between 2 and 10 per cent, the higher the concentration the shorter is the time of the treatment.
3'hc equation representing tile case in which a conceiitrated iiitric acid is used shows tliat iron is highly oxidized, forming ferric oxide, and tlierefore promotes corrosion. Summary
Dilute iiitric acid in alcoholic solution, like clrromic acid, will produce a prot,cct.ive film on iron, This film is highly triiit to corrosion by wat,cr, especially wlren the moisteiind iron is placed iir air free from carbon dioxido. 1 lie experimental evidence indicates that the protective film 011 the iron is produced by an oxidized product of iron fimricil by the dilute nitric acid in alcoliol. This oxide must be in a ferrous condition, for soluble ferrous hydroxide, being alkaline in nature, makes iron passive. , \
Acknowledgment
The autlior desires to express his sincere appreciat,ion to Prof. Albert Sauveur for the interest taken in this work, aiid to extend Iris thanks to E. 1,. Reed and L. It. Van Wert for their valuable assistance.
Effect of Ozone upon Oils' By M . V. Dover and R. B. Appleby uNoir;riKxr\rc ExrauisleNInL S i i r i o s , l!NIY.*SIIY
oil M'SSSOUKI,
Coi.u\rar~,Mo.
A B Figure 3--Commercially Pure Iron Ernwed to the Atmosphere in e Corroaion Test for 2 Weeks A- Rtched lor 30 rmnutes with 5 per cent HNOi in alcohol before expouure. B-Unetched
' h e reason for these conditions bas been explained as follOWU:
(1)
'
Using dilute nitric acid: Fe 2HNOs = Pe(NOs)* H, Fe(NOs)* HI = FeO 2N02
+
ZFe(NOJ2
+
+
+ I40 (alcohol used) + HZ = Fea08+ H30 +(water 4N01 used) +
(2) Using concentrated nitric acid: 2Fe 2HNOa = Fez00. H,O
+
+
C;l':VEIUL oils liave been treated with ozoiie for varying leiigths of time and the effect upon some of tlie constants, as well as iipon bhe efficiency of eaalr of the oils when used as a lubricant, has been measured. The results so far obhiiied are noted briefly and in a qualitative way, in the aeeompanying table. The authors liope to ascertain, by work now in process, not unly tlie eEect of ozone and otlier reagents upon constants of oils aud upon their respective efficiencies as lubricants, hiit also wlietlier any definite relation exists between these comstants and the lubricating efficiency of the oils. The static coefficient of friction of each oil was determined by incans of a Decley Macline. The following formula was us'$: F = --.. L'x L where .F is the static coefficient of fraction, IZ the reading on t,he scale, C the constant of the macliine, and L the load in pounds per square inell. The efficiency of the oil as a lubricant is found from the coefficient of friction by thc following relation:
(A)
(B)
+ 2x0
Noies-(I) The rpeeimcn must be washed thoronghlg with water in order to obtnin a snti3fectory result. (21 The right-hand side of these equations has been tested ?ut hy using potassium ferrocyanide for ferric iron and potassium ferricyamde fur ierrour iron.
Efficiciicy = 100-((static coeffcicnt X 100J2
\Virile the variations in constants of tlie oils with reference to the times of treatment with ozone are not regular, nevertheless, tire generalizations given in the table are in the main true. EBciency
. .. ..~ .... Index ol rrlraction not much affected by trcatmeuts with ~ SP.+'" .I
a':,fnl
cn.
Figure 4-Apparafus for Making AIr Free from Carbon Dioxide
f l y comparing the two equations in the case when dilute
nitric acid is used, it is evident that Equation A represents the action under a reducing condition, whereas Equation I3 shows the action under an oxidizing condition. Ferric oxide does not produce a protective film in contact with water as ferrous oxide does, and therelore metal undergoes corrosion.
D I I O U L
It is thus seen that the addition of ozone causes, in each of the oils, decrease in iodine number, increase in acid number, increase in specific gravity, increase in viscosity. In the case of olive oil there is increase in interfacial tension, and decrease in surface tension, together R4t.h decrease in efficiency. I n the ease of Velocite H there is decrease in iiiteifacial tension, increase in surface tension, and increase in efficiency. Renown lhginc Oil follows the same trend a8 Velocite B, the effect, bowever, being less marked. 1 1
Received October 29, 1923. Prac. Phys. Sur. London. 91, Pt. 11. 26 (1920).
