t 



11, 



Dr. Redtenbachejroft;# Class of 'Organic Acids. 505 



* . 

 perfectly from one another}- taking only the middle portion of 



each. 



I had originally intended only to undertake the examina- 

 tion of the volatile acids of butter, but the form of the barytic 

 salts led me to the expectation and to the discovery of the 

 intervening acids. If the crystallization of the four volatile 

 acids of butter be compared, it is found that they all crystal- 

 lize in forms which are only of different sizes and differently 

 grouped. The prisms of caprate of baryta are microscopi- 

 cal, and appear like fine powder. Those of caprylate of ba- 

 ryta are united in small grains ; the groups of the caproate 

 of baryta are much larger ; and the baryta salts of the butyric 

 acid crystallize in groups as large as hazel-nuts. The other 

 three intervening acids, whose factor n is not divisible by 4 

 but by 2, crystallize in scaly clusters of a pearly lustre, as is 

 already known to be the case with valerianic acid and cenan- 

 thylic acid. 



I will now give the analytical results of the series, begin- 

 ning with the lowest. It is to be observed, that in the ana- 

 lysis of bodies presenting so many difficulties, the results 

 cannot be expected to agree perfectly with the theory. 



1. Acetic Acid. — The silver salts were formed from crystal- 

 lized acetate of soda; it gave 69*19 per cent, of oxide of sil- 

 ver ; theory requires 69*46 -per cent. 



2. Metacetonic Acid. — As before mentioned, the mother- 

 liquor, from which the acetate of soda was crystallized, was 

 decomposed by sulphuric acid. An oily stratum was pro- 

 duced, which was distilled over. It began to boil at 110° C. ; 

 what came over from 120° to 140° was neutralized by ammo- 

 nia and precipitated with nitrate of silver, then boiled until 

 completely dissolved. On cooling, the silver salt was depo- 

 sited in small hard grains and druses, which blackened at 

 100° C, and at a higher temperature fused and decomposed. 

 It had all the other properties of metacetonate of silver. 

 0*242 grm. dried in vacuum gave 0*144 grm. silver; and fur- 

 ther, 0*203 grm. gave 0*1525 grm. carbonic acid and 0*057 

 grm. water. 



Theory. Experiment. 



6 eqs. Carbonic acid . . . . 450*0 19*89 20*49 



5 ... Hydrogen 62*5 2*76 3*12 



3 ... Oxygen 300*0 13*26 12*47 



1 ... Oxide of silver . . . 1450*0 64*09 63*92 

 1 ... of Metacetonate of silver 2262*5 100*00 100*00 



3. Butyric Acid. — The oily acid just mentioned under 

 metacetonic acid as passing over at 140° to 164° C. was sa- 

 turated with baryta and crystallized. The first two crystal- 



Phil. Mag. S. 3. No. 197. Suppl. Vol. 29. 2 M 



