484 PHILOSOPHICAL TRANSACTIONS. [aNNO I7G7. 



stances; what substances they mix easily with, and to what bodies they prove a 

 menstruum, or assist in dissolving. 6. How far they agree in their virtues and 

 properties with the neutral salts made with mineral acids, and with each other. 

 7. What effects they have on the human body ; whether they promote more par- 

 ticularly the perspiration or the secretion by the kidneys, or whether they act 

 more readily on the bowels, and promote the discharge by stool ; and to ascertain 

 the exact and proper doses of each. 8. And lastly, what effects fermentation 

 and distillation have on native vegetable acids; and to observe and compare the 

 appearances of the neutral salts made with these acids in their different states; 

 viz. 1 . In their native state. 2. When made into wine. And 3dly, when made 

 into vinegar; and likewise when made with acids brought over by the force of 

 fire, or distilled from the same juices in each of the 3 different states mentioned. 

 And in order to facilitate their labours, Dr. M. concludes this long paper with 

 observing. 1st. That all vegetable juices, used for making neutral salts, ought 

 to be strained through a cloth, and then filtered through paper, before they are 

 saturated with the alkaline salt; and that, after they are saturated, they ought 

 to be allowed to stand for some days, and some of them for weeks, and then be 

 filtered again, before they are evaporated. 2dly. That it is of use to clarify many 

 of these juices, after being saturated, with the whites of eggs. Sdly. That it is 

 sometimes easier to obtain a neutral salt, by evaporating with a boiling heat, 

 than with a slow or gentle fire; as the heat of boiling water coagulates, and 

 throws up a quantity of viscid juices to the surface, which cannot be easily sepa- 

 rated by any other means. 4thly. That the sweeter any fruit is, and the more it 

 abounds with saccharine or viscid juices, the more difficult it is to obtain a neu- 

 tral salt; and for this reason he had not hitherto been able to get any neutral 

 salt from the saturated juices of pears, or of cherries. 5thly. That, in cases 

 where we are obliged to employ water mixed with the fruits cut small, instead of 

 their juices, it is right to peel off the skins before we attempt to saturate the 

 acid ; otherwise the alkaline salt is in danger of uniting with, and rendering so- 

 luble in water, the gross oils with which the skins generally abound, which after- 

 wards prevent the crystallization of the neutral salts.* 



L. Experiments on the Distillation of Acids, Volatile Alkalies, &c. showing how 

 they may he condensed without Loss, and how we may thus avoid Disagree- 

 able and Noxious Fumes. By Mr. Peter Woulfe, F. R. S. p. 517. 



In the common manner of distillation, there escapes a great quantity of fumes, 



* Though in these experiments Dr. D. Monro omitted to employ all the modes of investigation 

 which should have been resorted to, for the full ascertainment of the object in view ; yet it cannot 

 be denied that he is entitled to the merit of showing, though imperfectly, what was afterwards so 

 clearly demonstrated by Scheele, that there are several distinct species of acids in the vegetable 

 kingdom. 



