DR. BOSTOCK ON GOULARd's EXTRACT. 7T 



7. A folutlonof gum Arabic was formed, in the proportion Gnmprecipi- 

 oV one pari of gum to 100 parts of water* One-grain of this lord's extraaf 

 folution was added to 39 grains of water, fo thatthe gumonly 

 coiiftituted -5^*^-5 part-of the folutioiy; a fiugle grain of Gou- 

 lard dropped into it produced a perceptible opacity. 



8. Twenty grains of tlie faturaled folution of the acetate of — but fcarcely by 

 lead, had one grain of the folotion of gum added; the effeA^"^*'^^ 0^" ^'*'^- 

 was barely vifible, certainly lefs than in the former experi> 



nient. ^ ■ 



I am far from confidering thefe experiments as fufficient to 

 afford a complete inveftigation of the fnbjeft ; but I think they 

 may enable us to m»ke fome advances towards the truth. 



The 40 grains of the folution No. 1. contain 1 1.6 grains of Forty grains 

 acetate of lead; by the addition of the alcali, this was con- acetate contain 

 verted into eight grains of the carbonate of lead. Thefe eight u^ lead, ™*^ ^ " 

 grains of carbonate coniift of 6.72 grains of the yellow oxide, 

 and 1.2s grains of carbonic acid.* The 6.72 grains of yellow 

 oxide coniifi of 6.12 grains of pure lead, and .6 grains of ox- 

 igen, f fo that the 40 grains of the faturated folution contain 

 a little more than 6 grains of pure lead. 



By employing the fame reafoning to the analogous experi- forty grains 

 ment with Goulard, we may conclude, that the 11 grains of ^j"^J''^^°"^^^ 

 carbonate produced in this cafe, confifl of 9.24 grains of the * 

 yellow oxide of lead, and 1.76 grains-of carbonic acid; the 

 9.24 grains of oxide will be compofed of 8.4 grains of pure 

 lead, and .84 grains of oxigen, fo that the 40 grains of the 

 aqua lithargyri acelati contain nearly 8 1 grains of pure lead. 



We flmll not find it fo eafy to afcertain precifely the quan- Dedu£b*on of 

 tity of acetic acid which enters into the compofitlon of the ^^^ refpeftive 

 acetate of lead, and the aqua lithar^ri acetati \e{^G6\^\vdy i^^^^^^^^^ 

 but if we truft to the experiments of M. Thenard X, we muft 

 conclude that 11.6 grains of acetate of lead, contain about 

 three grains of the acetic acid. The quantity of acid in the 

 (Uj. lull, acet, is lefs than that in the acetate of lead, in the pro- 

 portion ot 40 to 60; thexefore the 40 grains of aq, lith, acet, 

 will only contain two grains of acid. 



Hence it follows, that 40 grains of the folution of acetate of Component parts 

 lead confi/l of, of each. 



* Thomfon's Chem. III. 50. f Prouft, Journ. de Phyf. 



LVI. 206. I Nich. Journ. VI. 223. 



Lead 



