LOW turnover in Hang Seng Index futures in mixed sentiment left the August contract with little support yesterday. Volume amounted to 6,108 contracts. The August contract fell 110 points to 9,510. This was compared to a cash market fall of 64 points to 9,537. The September contract lost 70 points to close at 9,545, in generally lacklustre trading. Index option trading was also weak with 1,292 lots traded. Jardine Fleming said: ''Sentiment was mixed dominated in the options market with trading concentrated on the puts.'' Overseas bulls sold August 9,200 puts while bears bought September 9,000 puts, said the brokerage. Open interest confirmed on Friday was stable in option and futures. In August futures, it was 33,252 contracts and in September it was 761. In index options the open interest in August call and puts was 5,467 and 4,948 lots respectively. In September it was 11,178 and 10,963 lots respectively. In December it was 846 and 1,688 lots respectively. Implied volatility in the front month was at 30 per cent, marginally up on Friday's level. Historic 100-day volatility was around 33 per cent on the Hang Seng Index.