292 Chemical Preparations. 



purpose, others will judge. My first object was to obtain a per- 

 fect and clean solvent for caoutchouc. My second one will ap- 

 pear by and bye. Take sulphuric acid (and water ?*) equal weights, 

 mix, and when cold add a quantity of it to a quantity of oil of 

 turpentine, and agitate thoroughly : the acid will become colored 

 by uniting with, or charring the resin ; let. the acid subside, and 

 decant the clear spirits. Repeat the operation until the acid sub- 

 sides without being discolored. The oil of turpentine thus pre- 

 pared, with warmth and strong solar light, is, as I believe, a per- 

 fect solvent of caoutchouc. This process is somewhat expensive and 

 troublesome, and after a great number of fruitless trials with various 

 articles, I found that alkalies and alkaline earths, especially lime, 

 would attack resin, but not pure oil of turpentine. On distilling oil 

 of turpentine from caustic lime and water, I found a great deal of re- 

 sin remaining in the still on the first operation, but none at any sub- 

 sequent one ; hence the resin was an adventitious body. I likewise 

 found, by the sulphuric acid test, that the oil was pure ; and I like- 

 wise found that the oil thus purified was not a good solvent of caout- 

 chouc, probably because in distilling the oil it had acquired water 

 which it held in combination. 



3. Safe process for manufacturing gun powder. 



I have always supposed that gun powder, the materials being the 

 same, was good in proportion to the intimacy with which its compo- 

 nent parts were united. The almost infinite subdivision of paints 

 effected by grinding them in oil, it appeared to me might be imitated 

 by grinding the materials composing gun powder in some fluid, in 

 which these materials were insoluble. Nitre and charcoal are insolu- 

 ble in alcohol, and sulphur is nearly so; hence in a properly constructed 

 mill these substances may be ground in alcohol, and the greater part 

 of the alcohol drained and pressed out, whilst the small residue will 

 evaporate with great readiness. I made the experiment, and obtain- 

 ed a good powder at the first operation. Alcohol, however, w^as rather 

 too volatile, and a substitute that was less so, was a desideratum. This 

 substitute was found in pure oil of turpentine : the resin having been 

 previously completely removed, the oil when used was readily evapo- 



* The author has, in his MS., omitted to state what is mixed with the acid : we 

 have ventured to fill the void as in the text ; for the strong acid would blacken and 

 <5:har the oil of turpentine. — Ed. 



