96 Dr. Wrightson on the Atomic Weight and 



2 and 3 oz., and formed three-fourths of the entire quantity. 

 It was nearly pure propionic acid, as shown by the following 

 baryta determination in the baryta salt. 



0*1225 grm. of the salt, after once recrystallizing and then 

 dried at 100° C, afforded 00994 grm. of sulphate of baryta 

 corresponding to 53*3 per cent. BaO ; theory requires 53*8 per 

 cent. 



That portion of the fluid which distilled over between 152° C. 

 and 180° C, i. e. the entire residue, was so small that no pro- 

 duct having a constant boiling-point could be separated by frac- 

 tional distillation : the greater part was still tolerably pure pro- 

 pionic acid. Analysis gave 50*0 per cent, carbon and 8 per cent, 

 hydrogen. The hydrate of propionic acid requires 48*6 carbon, 

 and 8*1 hydrogen. 



The Oily Acid insoluble in Water. 



The oily fluid smelling like caproic acid, which was dried over 

 chloride of calcium, was rectified by once distilling, and then 

 subjected like the first portion to fractional distillation. It 

 began to boil at 130°, a small quantity of propionic acid and 

 water going over ; the boiling-point then rose gradually and 

 uniformly to 196°-198° C, at which temperature it remained 

 constant until about half the fluid distilled over as pure caproic 

 acid. Towards the end of the distillation the temperature rose 

 about 7° C, and the residue in the retort began to blacken. The 

 portion distilled over between 130° and 196° was again rectified, 

 and that part received between 155° and 175° C. put aside. 

 This operation was repeated several times, the thermometer each 

 time approaching nearer to a medium temperature between the 

 boundaries indicated. The product from the fourth distillation 

 between 165° and 172° C, about 7 or 8 grms. by weight, still 

 showed no constant boiling-point, nor could any such be observed 

 in any part of the acid distilled between 130° and 198° C. 



If in the metamorphosis of the cyanides of scthyle and amyle 



by the action of potash the new acid C 9 H 9 O 4 had been formed, 

 then the boiling-point should have been between that of butyric 

 and valerianic acids, i. e. about 166° C. 



For this reason I examined the fluid obtained between 165° 

 and 172° very carefully, although the uniform rising in its boil- 

 ing-point gave sufficient proof that I had not a simple acid in my 

 hands, but most probably a mixture of two. 0*1568 grm. of the 

 fluid by combustion with oxide of copper gave 0*3166 grm. of car- 

 bonic acid =55*06 per cent, carbon. The acid C 9 H 9 O 4 would 

 contain the same quantity per cent, of carbon as a mixture of 

 equivalent weights of propionic and caproic acids, i. e. 56*8. To 



