Posted By Ian Bruce I have recently investigated an accident involving some pupils at a school who ingested "Lime Water" during a science practical. I'm lead to believe that lime water is Calcium Hydroxide and that it is non-harmful in a very dilute form. There are lots of issues surrounding this incident, risk assessment suitability, competence, PPE etc but my problem is, I'm not a chemist! Is the above information correct? Can anyone advise? Any replies gratefully received.

Posted By Graham Bullough I'm not a chemist but know a good source of advice, namely the CLEAPSS School Science Service which provides good practical comprehensive information about matters pertaining to school science and also technology. I recall that CLEAPSS said at their AGM last July that all LEAs in England & Wales were members, so your LEA should be a member. Your LEA science adviser, assuming there is one, should be able to confirm. If it already is, the science department where the accident happened should possess the relevant information anyway, - which you could also use to investigate e.g. how did the pupils come to ingest the solution, and did the department/teacher have and follow any relevant risk assessments? If your LEA is not a member, the annual membership fee is worth its weight in gold in relation to what CLEAPSS provides, including its telephone helpline, handbooks and information for direct use by schools. (p.s. In case anybody wonders, I don't get any commission from CLEAPSS! I simply have no hesitation recommending it because it provides an excellent not for profit service, has played and continues to play a major role in the generally high standard of health and safety during the teaching of science in schools.)

Posted By Robert K Lewis I think I might probe this further. Whilst all the statements above are true I am wondering whether this was freshly prepared as part of a larger experiment. Lime water is obtained by the slaking of Calcium Oxide with water. This is highly exothermic often resulting in significant spitting. The liquor then has the solid in suspension which is filtered off - this is more corrosive and you may know it as slaked lime. The calcium oxide is produced in the lab. via high temperature treatment of calcium carbonate. What if any of these procedures were being done. You may only be told the end story!! Like all incidents this is a part picture. I also agree that the reasons for the swallowing at all must be investigated. Has someone suggested that it was OK? Bob