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Five experimental petroleum extracts were produced from luboil distillates derived from Middle East paraffinic crude by solvent extraction and severe hydrotreatment. The polycyclic aromatic content (PCA) of the extracts was determined by dimethyl sulphoxide extraction and ranged from 3.7-9.2% w/w. The five extracts were evaluated for their potential to induce cutaneous and systemic neoplasia in female mice derived from Carworth Farm No 1 strain (CF1). The test substances were applied undiluted (0.2 ml per application) to the shorn dorsal skin twice weekly for up to 78 weeks, with 48 mice in each treatment group and 96 in the untreated control group; two further groups, each of 48 mice, were similarly treated either with a non-hydrotreated commercial aromatic extract (PCA content, 19.7% w/v) or with a low dose of benzo(a)pyrene (12.5 micrograms/ml acetone). The mice were housed individually in polypropylene cages in specified pathogen free conditions. The incidence of cutaneous and systemic tumours was determined from histological analysis of haematoxylin and eosin stained tissue sections. The results were correlated with the PCA content of the extracts and compared with those from female mice exposed to a non-hydrotreated commercial aromatic extract. Four of the hydrotreated extracts were carcinogenic for murine skin; the two products with the lower PCA contents were less carcinogenic than the products with the higher PCA contents and all were less carcinogenic than the commercial extract. One extract with the lowest PCA content was non-carcinogenic. Thus refining by severe hydrotreatment was an effective method of reducing the carcinogenic potential of petroleum aromatic extracts. Although other physicochemical properties may influence the biological activity of oil products, the PCA content determined by dimethyl sulphoxide extraction may be a useful indicator of the potential of oil products to induce cutaneous tumours in experimental animals. There was no evidence that the commercial or hydrotreated extracts increased the incidence of systemic neoplasms when applied twice weekly to the dorsal skin.

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KONINKLIJKE/SHELL-LABORATORIUM, AMSTERDAMDuring the last few years, dimethyl sulfoxide has been increasingly applied as a highly selective solvent for extracting polar or polarizable compounds from a non-polar medium 192t3. In this connection, we briefly report about our experience with (CH3)zSO as a solvent for U.V. absorption measurements.During an investigation into the composition of white mineral oils, we extracted sub-traces of polyaromatics from the oil sample in hexane by means of dimethyl sulfoxide, according to the procedure of Huenni et ~1 4 9 5 1 6 . The total polyaromatics concentration was estimated by subtracting the U.V. absorption of a blank from that of the extract. The reproducibility of this procedure appeared to be poor; moreover, even weakly negative values were no exception.We found that the poor results are mainly due to the fact that dissolved oxygen considerably raises the U.V. absorption of dimethyl sulfoxide (see Table I). Thus, serious errors may result when extract and solvent blank do not contain equal quantities of dissolved oxygen. Stripping of dimethyl sulfoxide (in a Teflon-stoppered quartz cell) with dry, pure Nz or COz, prior to U.V. absorption measurements, eliminates the effect (cf. Table I). Incorporating this procedure into the method described by Huenni et a1 4,516 leads to a good reproducibility.

Paraffin Reinheitsforderungen Analysen-MethodenIn der Publikation : ,,Die gesetzlichen Verordnungen iiber Reinheitsanforderungen fur Paraffin und Mikrowachse in den verschiedenen Landern" hat G. TITWHACK [I] einige Aspekte der Analysenmethoden in Deutschland, USA und GroDbritannien miteinander verglichen.Gern mochten wir hierzu auf unsere inzwischen erschienene -4rbeit [z] hinweisen, in der ein wesentlich ausfiihrlicherer Vergleich nicht nur der Prinzipien und Empfindlichkeiten der Methoden, sondern auch der technischen Einzelheiten bei der Analyse verschiedener Hartparaffine und Mikrowachse durchgefiihrt wird. Dadurch wird ein ganz anderes Licht auf die Zuverlassigkeit der dentschen und der USA-Methoden geworfen. Bei der technischen Durchfiihrung der Methoden des Deutschen BundesgesundheitsamtesReinheitsquaiitat liefert. Schwefelsaure-Raffinierung kann fur Mikrowachse selbstverstandlich nicht angewandt werden, da eine Trennung vom entstandenen Saureteer nicht erfolgt. L i t e r a t u r[I] TITSCHACK, G., Nahrung TO, 77 (1966).[ z ] RIAZEE, W. M., €I. R. GERSMANN u. A. VAN DER WIEL, Food and Cosnietics Toxicology 4. 17 (1966).