THE JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY
280
acid values. All of the resins which had been heated to fusion dissolved readily and completely in the mixture of alcohol and benzene, and gave results which are presumably correct. APP.4RATUS
The apparatus used in these experiments is shown in the accompanying figure. The resin was contained in a !age test tube (1 in. x 8 in.). This tuhe extended, through a piece of asbestos board, into a hemispherical iron pot which was heated by a MBker burncr and served as an air bath to secure uniform heating of the resin in the tube. An accurate thermometer wm used to indicate the temperature of the resin in the tube, while a second thermometer placed beside the tube served to indicate the temperature of the air bath. A weighed amount (usually about 10 g.) of the resin was heated in the apparatus until melted. The heating was then continued at the rate of 3" C. per min. until the desired final temperature was at.tained. The resin mas kept a t the final temperature for 5 min. The meltcd resin was stirred from time to time to insure uniform heating. Tube and resin were removed from the air bath and cooled rapidly by holding in a blast of air and finally by immersing in cold water. The final product was weighcd and analyzed.
Vol. 14, No. 4
These changes may be assumed to be due to several different types of reaction which may occnr simultaneously in the heated resins. Either polymerization or absorption of oxygen a t the unsaturated groups would decrease the iodine number; while cracking or depolymerization would increase the absorption of iodine. Worstall has shown that when finely powdered copals are allowed to stand in the air, oxygen is absorbed and the iodine values decrerse. This absorption would presumably take place more rapidly at elevated temperatures, and would account partly for some of the observed changes. On the other band, the volatile products formed during the "running" of varnish resins cont.ain relatively large amounts of hydrocarbons which are obviously produced by the cracking or partial depolymerization of the resin substance. Apparently the direction and the extent of the change in iodine value are determined by the relative extent to which these various reactions-oxidation, polymerization, cracking, and depolymerization-oceur in the heated resin; this, in turn, will depend on the nature of the resin and upon the temperaturc to which it hay been heated. There is no apparent relation between the loss in weight on heating and t h e change in iodine number or the change in acid value.
RESULTS The results obtained in these experiments are shown by Tables I, 11, aiid 111. TABLEI-CRIINCE
IN ACID NUMBERS
Oriainal
Congo coprl ................ Kaum ...................... East Indian copal., , , , , Manilacopal ............... Poniianak ...................
. . . ..
TIRLB
II-CNaacs
176
129 66 169 176
Acid Value after Heating t o C. 350' C. d90" C. 136 104 98 100 90 72 Pa 36 24 156 187 132 1x2 115 101
Iodine Number (Hubl) after Hcatlne to Ori~inal 300' C. 3.50" C. 390' C. CDngocopni . . . . . . . . . . . . . . . . 126 la9 97 96 Kauri ...................... 112 115 104 104 East Indian E O P ~ , 75 7s 90 1M Manilacopnl.. . . . . . . . . . . . . 117 122 122 116 Pontianakcopal ............. 120 124 122 96
.........
IN
By R. I). Scott S16m D B P I I R T Mop B ~HBA~.TI%. Cowxltvs, Oaro
300O
EN IODINL? V I L U l i S
TABLSIIT-Loss
Fat Extraction Set'
WIICIIT
Percentage Loss after Heating to
swo c .
350- c.
390- 0.
The fat extraction set described has proved very satisfactory for stock feed and other routine analyses. The cabinet and condensing tank were made up by a local tinsmith from 16-0s. tinned copper. The cabinet is 48 X 18 X 4.5 in., and the condensing tank, 47.5 X 4 X 4 in. The twelve condenser tubes are of 3/a-in. block tin, each 30 in. long, and lie in the position A-A. Eeat is provided not by hot plates, but, by "space heaters," heating strips obtainable a t electrical supply houses at about one-tenth of the cost of an electric hot plate. The two used are rated at 125 volts, 4 amperes, and when connected in series give the proper heat to boil ether, the bottom of the flash being 2 in. above the heaters.
I t will be observed that in every case the heat.ing of the resin results in a marked decrease in the acid value. This is presumably due to the splitting off of carboxyl groups and the evolution of water and carbon dioxide. This hypothesis is supported by the observation that water and carbon dioxide are evolved during the "ronning" of varnish resins. With Congo and Manila copals the decrease in acid value is substantially complete at 350" C., while kauri and Pontianak copal show further marked decrease in acid value with increased temperatures of heating. The different resins gave markedly different results for the change in iodine value on heating. With Pontianak and Manila copals the iodine value increased somewhat at 3W"C., shouTed little further change a t 350' C., and decreased again a t 390' C. Kauri, after heating to 300' C., showed an inThe flasks, thimbles, and outer glass tubes form the concreased iodine value, but further heating resulted in a d e crease to below that of the original resin. The iodine value ventional Vivian type fat extractor, but porous clay thimbles of Congo copal deareased as the temperature increased, are used instead of glass tube thimbles covered at the bottom while that of East India copal increased progressively_with with a filter paper supported by muslin. the temperature. 9 Received Decemhei S, 1921.
