Shopkeepers should record the names and identity card numbers of people who buy acid to help police to narrow the pool of suspects in the event of future attacks, Yau Tsim Mong district councillors suggested yesterday. A registration system would also act as a deterrent, they said. However, academics were sceptical about such a system, saying it would be of little use to police and be difficult to implement. The call for a registration system was made during a meeting of the Yau Tsim Mong District Council to discuss the effectiveness of installing spy cameras to prevent acid attacks. District councillor Chan Wai-keung, who put forward the idea, said it would help police track down people who bought acid. 'Acid is a very dangerous thing. It's just like guns in the US,' Chan said. Councillor Benny Yeung Tsz-hei suggested the government put in place a system that required retailers to put unique labels on the bottles, saying this would make it easier to investigate an attack. However, academics questioned the feasibility and effectiveness of a registration system because acid was widely used for cleaning toilets. Catherine Leung Lai-yee, a criminologist at Hong Kong Baptist University, said: 'There are too many people buying [acid to clean toilets] ... Almost every family has a bottle of it. It is not easy for police to find out who the attacker is by tracing who bought acid - the pool is too large.' She said the attacker might switch to other chemical substances if buying acid was made difficult. 'There are so many substitutes for acid that the government can't place regulations on all of them,' she said. Chemistry professor Allan Cheung Shi-chung, of the University of Hong Kong, said a registration system for the purchase of acidic toilet cleaners would see the product disappear from the market. 'Acid is very cheap at the moment. People will not bother to go through so many procedures to buy it. They will simply turn to substitutes,' he said.