Volatiles formed on heating clay minerals contain a variety of cations and anions and are highly reactive. Gas chromatograph-mass spectrometer analysis of long-chain n-alkanes exposed to such volatiles showed that some decomposition occurred even <250°C. Reactions with anions donated by the volatiles led to compounds containing atoms other than C and H, e.g., Cl. The products obtained from n-alkanes heated in a stream of clay volatiles to 500°C resembled those produced by corresponding alkane-clay mixtures heated to 250°C. At higher temperatures contact between the alkanes and montmorillonite or halloysite led to changes in the assemblages formed, whereas kaolinite or sepiolite had no effect. Thus, the first reactions that occurred when clays were heated with n-alkanes were apparently induced by the volatiles; at higher temperatures catalysis due to direct contact came into play with some of the clay minerals.

An experiment was conducted to determine if molasses could be successfully used to administer dotriacontane (C32) and hexatriacontane (C36) n-alkane markers to steers and to compare this method with a commercially available intra-ruminal controlled release device (CRD). The experiment was conducted over two similar periods (runs) using 24 Brahman crossbred steers in each run to study the effect of marker delivery methods and tropical grass hay diets in a randomized complete block design with three replicates. All steers were housed individually in partially covered pens, received one of two buffel-grass hays (B20: 20-week regrowth; 0·72 g nitrogen (N) per 100 g and B8: 8-week regrowth; 1·11 g N per 100 g) and one of four marker delivery treatments (control: no marker; 200 mg/day of C32 and C36 n-alkanes from a CRD or offered three times (Ms ✕ 3) or five times (Ms ✕ 5) a day in molasses). Voluntary intake (VI) and dry matter digestibility (DMD) for diets differed (P < 0·001) with B8 greater than B20. There was no difference among marker treatments for VI but the control treatment had greater, unexplained and possibly spurious, DMD than the Ms ✕ 3 marker treatment. Although the recovery of n-alkanes was variable (0·84 to 1·05) adjacent odd- and even-chain n-alkanes were similar with no differences (P > 0·05) due to marker treatment or diet. The CRD supplied a consistent marker dose between 6 and 18 days after insertion. Deviation from the 24-h mean faecal concentration seldom varied more than 0·03 for the individual markers and 0·05 for C31/C32 and C33/C32 ratios for all treatments. Over all the n-alkanes studied, the between-day variation was less than the within-day variation. For instance, the average of subsamples taken at 06:00 h and 18:00 h was within proportionately 0·05 of the 10-day mean concentration for 0·38 and 0·25 of records for C32 and C36 markers, respectively. It was concluded that molasses containing C32 and C36 n-alkane markers and given either three or five times daily was as accurate as the commercial CRD in administering n-alkane markers to steers and provides a method of delivering n-alkanes over an extended period in grazing studies.