INDUSTRIAL AND ENGINEERING CHEMISTRY
884
sec-butyl mercaptan. A 50-cc. portion of the carefully separated benzene layer was shaken with 50 cc. of 3 per cent hydrogen peroxide solution, which was added in small quantities a t a time. The insoluble product is a t first brownorange, then paler and, when dry, of a yellow-orange color, which is common for the peroxides. The analysis (constant weight) gave 70.5 per cent Pb and 5.0 per cent S; Pb : S = 1 :0.45. Thus the substance is not chemically uniform. With this procedure the benzene, after all the insoluble products have been filtered off, remains slightly colored. If, however, only half the above volume of hydrogen peroxide solution is used, the benzene layer is obtained colorless. When some of the yellow oxidation product is evaporated to dryness to destroy all hydrogen peroxide, it gives the per-
Vol. 22, No. 8
oxide reaction on potassium iodide-starch paper if moistened with concentrated hydrochloric acid, but not with water. I n this it resembles the peroxides formed by oxidation with atmospheric oxygen though its composition is different, If hydrogen peroxide is added in sufficient excess, the formerly yellow substance is transformed into a white substance, which is but little soluble in water. This may be basic lead sulfonate. Literature Cited (1) (2) (3) (4) (5)
Manchot and Gall, Ber., 60, 2318 (1927). Morrell and Faragher, IND. ENG. CHEM.,19, 1045 (1927). Ott and Reid, I b i d . , 22, 878 (1930). Ott and Reid, I b i d . , 2'd, 884 (1930). Szent-Gyorgyi, Biochem. Z.,146, 245, 254 (1924).
Reactions of Lead Mercaptides with Sulfur' Emil Ott2 and E. Emmet Reid3 CHEMISTRY LABORATORY, J O H N S HOPKINSUNIVBRSITY, BALTIYORE, MD.
F TO a solution containing lead mercaptide elementary sulfur is added, a well-known change takes placeleading to the formation of a dark-colored insoluble product, assumed to be lead s u l f i d e . T h e r e a c t i o n is commonly written Pb(SR)Z S =
I
+
PbS
+ (SR)2
The reaction of lead mercaptides with sulfur in Actually it has been possisolution has been studied. It was found that the ble to obtain c o m p o u n d s reaction is not simply formation of lead sulfide, as corresponding to RS.Pb.8.generally assumed, but is more complex, leading to Pb.SR in the case of secondcompounds of the type PbS, P ~ L S ( S R )P Z~, Z ( O H ) Z S ~ary ~ and normal butyl merPbz(OH)& as well as mixtures of these and others. captans. These products are It is shown that all the experimental data are most brown when dry and correreadily understood if the formation of unstable polyspond to the well-known sulfides is considered as a first step followed by dePb2SC12, which may be obcomposition of these intermediates. tained from lead c h l o r i d e
(1)
showing the formation of lead sulfide and alkyl disulfide (1). The present investigation shows that the reactions involved are by no means so simple as here represented. It has been possible to isolate intermediates indicating a more complex reaction. These decompose rapidly and it is not always possible to duplicate results. I n some cases analyses have indicated definite compounds, but in most cases they point to mixtures. Emphasis is put on the existence of such compounds rather than on any particular formula. It appears reasonable to compare the lead mercaptides with other hydrogen suliide derivatives, and iherefore to assume that the reaction with sulfur may lead to intermediate formation of unstable polysulfides. The following reactions may be imagined : Pb /SR S 'R
+
P b < F +
S-SR S +Pb+P
