228 Dr George Wilson on the 



niently operated on at once. The reduction of the blood 

 to ashes was a tedious and not very pleasant process, but 

 with the help of a powerful furnace, and the active co-opera- 

 tion of my assistant, Mr Stevenson Macadam, who took great 

 pains with the whole preliminary operations, I succeeded in 

 the course of a month in reducing the whole quantity to well^. 

 burned ashes. 



These ashes contained some unburned charcoal, but not 

 in large quantity ; in greater part they presented the appear- 

 ance of two distinct substances ; the one a dark-red solid, 

 owing its colour to the presence of peroxide of iron, the other 

 a white fused salt, having a strong, pure, saline taste, and 

 consisting in gi^ater part of chloride of sodium. The pre- 

 sence of this substance interfered with the detection of 

 fluorine, by evolving a large volume of hydrochloric acid, 

 when the ashes were treated with oil of vitriol, which carried 

 away the hydrofluoric acid evolved simultaneously. It was 

 necessary, accordingly, to remove the chloride of sodium be- 

 fore seeking for fluorine ; and to avoid the risk of introducing 

 the substance sought for, by the employment of reagents which 

 might possibly contain it, I effected the removal of the salt by 

 simply digesting the powdered ashes in a minimum of distilled 

 water. This risked the removal of a little fluoride of cal- 

 cium, or any other soluble fluoride which might be present, 

 but precluded the possibility of any such compound being 

 added to the ashes. After being washed accordingly, they 

 were dried, and warmed with oil of vitriol in a lead basin, 

 covered by a square of waxed glass, which had the words, 

 " Blood, 5th July 1850," traced upon it by a blunt &tyle in 

 the ordinary way. The whole of the ashes were employed 

 with one piece of glass ; but as the vessel could not contain 

 the entire quantity in one charge, it was divided into two 

 portions, the first of which remained for five days in the 

 basin, and was then replaced by the other. The glass was 

 thus exposed for ten days continuously to the vapour arising 

 from the acidified ashes. They effervesced very slightly when 

 treated with sulphuric acid, but evolved a sharp acid odour. 

 The lead vessel was kept at a temperature of about 150° 

 Fahrenheit during the day, and fresh quantities of oil of 



