354 On Sponlancous Injlammatlons. 



that disaQ;reeabIe event. Care, however, ought always to be 

 taken not to put ashes newly burnt, and which are still 

 mixed with charcoal, in places where they may have a 

 communication with combustibles. 



The formation of a pyrophoric matter is remarked chiefly 

 hi the preparation ot"con)mon soda, which is obtained bv 

 the incineration ot several marine plants containing a great 

 deal of sulphate of soda, and which in burning furnish al- 

 w'ays a greater or less quantity of sulphur according to the 

 manner in which the operation is directed. 



The formation of the phosphurct of lime has great ana- 

 logy with that of the sulphuret of lime. Though the phos- 

 phoric aeid is not found so often in vegetables as the sul- 

 phuric acid, it however exists in them in much larger quan- 

 tity than has hitherto been supposed ; it is found chiefly in 

 the greater part of plants which grow in marshy places, in 

 turf, and in several kinds of white wood. By rechicing 

 tliese kinds of wood to charcoal there is sometimes formed 

 a small quantity of phosphorus, which may remain com- 

 bined with the same bases which retained the phosphoric 

 acid before the combustion : phosphorus, bv contracting 

 other combinations, may be no longer susceptible of pro- 

 ducing any accident ; but it may happen also, by the con- 

 currence of various circumstances, that charcoal impreg- 

 nated \\ ith anv phosphuret, when exposed to the action of 

 warm and moist air, will disengage phosphorated hvdrogen 

 gas, which by the contact of the atmospheric air may kindle, 

 and conununicate inflammation to the mass of charcoal. 



Two instances of this kind of spontaneous combustion 

 took place in the powder manufactory of Essone in the 

 years S and 10. The first time the fire broke out in the 

 box for sifting the charcoal, and the second time the char- 

 coal repository took fire, without room being left for sus- 

 pecting that it could arise from any thing but spontaneous 

 inliammation. The different reports on these two events* 

 were inserted in the public journals, but the explanations 

 given were not suflicicntly satisfactory. It appears very 

 probable thai they were occasioned by some phosphorus 

 contained in the charcoal ; and this explanation is the more 

 founded in reason, as the alder wood used at Essone as well 

 as in most of the powder man a factories, and which on many 

 accounts deserves the preference over other kinds of wood 

 tor the making of gunpowder, contains phosphoric acid ; 

 at least tliat which grows in our neighbourhood does. 



Charred turf begnis to be used in some manufactories, 

 a.nd for dlflerent operations ; but as it is much disposed to 



spontaneous 



