THE BARIUM ACID.
Reading edition
The resinous material used and spoken of as the “Barium Acid” is the material prepared and so named as given under the “Method of Separation”.
PHYSICAL PROPERTIES:—Dark reddish brown in color, syrupy in consistency and has a characteristic odor; heavier than water; soluble in benzol, ether, alcohol and acetone, but insoluble in petroleum ether and water.
This resin constitutes about sixty percent of the total ester resins; i.e. the resins left after the free acids have been removed with aqueous potassium hydroxide.
An analysis of the barium salt obtained by precipitation from the potassium soap was made and the following data obtained:—
Wt. of substance used 1.1715 .5860
Wt. of barium sulphate .4430 .2205
Barium equivalent .2606 .1298
Percent barium 22.2% 22.1%
The following method was used in making the above analysis. The weighed material was ignited in a platinum crucible by gently heating until the combustible gases formed were given off. The crucible was then more strongly heated to completely burn off the carbonaceous material left. The residue was extracted with nitric acid and the barium precipitated as the sulphate with dilute sulphuric acid, and the weight of the barium sulphate determined.
Expressed as the ACID NUMBER, or the number of milligrams of potassium hydroxide required to neutralize the free acids in one gram of the substance, the following data was obtained:—
Barium equivalent .2606 .1298
Barium expressed as KOH equiv. .2131 .1062
Wt. of material used 1.1715 .5860
Milligrams of KOH per gram 181.9 181.3
ACID NUMBER 181.9 181.3
The following gives the ACID NUMBER obtained by direct titration of the barium acid; in “A”, barium hydroxide was used and in “B”, sodium hydroxide was used.
A small quantity of the material was dissolved in a sufficient quantity of neutralized alcohol to give a liquid of a light yellow color, Phenolphthalein was used as the indicator, and the alkali was added until a red color was produced.
“A” “B”
Wt. of substance .6160 .2345
Cc. of alkalie 4.54 1.75
KOH equiv. per gram 41.40 41.90
Acid number 41.40 41.90
On evaporating a portion of the alcohol from the material left after titrating with the sodium hydroxide, and adding water to obtain an aqueous solution of the sodium salt, an emulsion was formed, and on standing globules of the free resinous acid separated. From the data thus obtained, it can readily be seen that the acid or acids which constitute the BARIUM ACID must have a number of carboxyl groups and form a different series of salts by precipitation than by direct titration. The salt or salts formed by direct titration, although neutral to phenolthalein may be acid in structure. This is further shown by the fact that the potassium salts produced by direct titration are readily hydrolyzed. The acid number obtained by the precipitation of the barium salt may be called the COMBINING VALUE, and the acid number obtained by titration the TITRATION VALUE.
A number of molecular weight determinations were made on the free barium acid. McCoy’s Boiling Point Apparatus was used and Merk’s benzol (free from thiophene) was used as the solvent. A weighing pipette with a bulb was used to introduce the material, the bulb being weighed before the material was introduced into the apparatus, and afterwards, the difference being the weight of the material used.
Wt. of pipette (before) 16.3670 14.8895
Wt. of pipette (after) 14.8895 12.4610
Wt. of material used 1.5225 2.4285
Original temperature 3.53 3.53
Final temperature 3.60 3.62-3
Change in temperature .07 .09
Volume of solution 37 cc 43.5 cc
Constant for solvent 3280 3280
Approx. Molecular Wt. 2000 2100 or 1800
Combustions were made using the barium acids. By qualitative tests it was found that the acids contained only carbon, hydrogen and oxygen. The following gives the results of the combustions.
Wt. of boat 2.8402 2.8402
Wt. of boat and resin 3.0500 3.0250
Wt. of resin .2098 .1848
Wt. of H2SO4 tube 78.0250 78.1415
Wt. of tube plus water 78.1520 78.2550
Wt. of water .1270 .1135
Hydrogen equiv. .0143 .0126
Wt. of KOH bulb 48.8140 51.7095
Wt. of bulb plus CO2 49.3800 52.2085
Wt. of CO2 .5660 .4990
Carbon equiv. .1543 .1361
Percent Hydrogen 78.5% 73.6%
Percent Carbon 6.8% 6.8%
Percent Oxygen 19.7% 19.6%
An attempt was made to make the potassium salts of the barium acids by saponification with alcoholic potash. A small quantity of the acid was treated with an excess of ten percent alcoholic potash and heated to eighty degrees Centigrade to complete the saponification. Instead of the formation of the potassium salts, a thick dark brown solid, gummy mass separated. On cooling it solidified to a brittle solid which had all the physical properties of a true resin. This solid is soluble in ether, chloroform and benzol, slightly soluble in alcohol and insoluble in petroleum ether and water. It burns without the formation of an ash. Evidently, this brittle material is a condensation product of the original barium acid.