Flash-point apparatus, c 1870s.
© Science Museum / Science & Society Picture Library
As mineral oils began to replace vegetable oils so the volatility of the new oils became a cause for concern. The flash-point apparatus on the left was devised by Sir Frederick Abel (1827-1902). Oil held in a cup is heated by a water bath. The oil is covered by a slide which has a small hole. A burning jet is periodically tilted into the hole when the slide is withdrawn. As the temperature rises, the point at which a small explosion occurs is called the flash-point.