480 ILt'DL'STRIdL A S D ENGINEERING CHEMISTRY Yol. 17, No. 5

tically all treatments, such as aging, oxidation, and polym- erization, bring about a splitting of these fatty acids from the glycerol. Thus it is seen that the acid numbers of both oils increase as the polymerization advances. This is explained by Coffey5 as due to the hydrolysis of the glycerides by water, traces of which are to be found in raw linseed oil.

C3H5-OL + ~ H Z O - C ~ H ~ O H ) ~ + HLn + HL + HSt

acid acid acid

/ OLn

\ OSt Glycerol Linolenic Linolic Stearic

At the high heats reached the glycerol is rapidly volatilized, so that, following the mass law, the reaction goes on towards completion. Moreover, the glycerol is continually being broken up into acrolein and water; the constant formation of the latter also aids in pushing the reaction towards the right.

The significant feature of the acid number curves (Figure 3) is the gradually increasing difference or spread between the oils from the copper and monel kettleswhich had been bodiedunder identical conditions. At first the amount of free acids in both oils seems about equal, but as the operation continues the increase in therate of formation of free acids in the copper kettle grows larger and larger than the corresponding increase in the monel batch. At the end of a constant increase the cop- per-boiled oil has an acid number 3.2 mg. higher than the monel-boiled oil.

It is known that metallic soaps2 of any kind will catalyze the acid-forming reaction described above, and that the rapidity of formation of free acids is proportional to the concentration of metallic soaps in the oil. Even minute quantities, too small to be detected by direct analysis, exert an appreciable ef-

6 J . Soc Chem I d , 40, 19 (1921).

feet. Hence the higher acidity of the oil boiled in contact with copper offers indirect but positive evidence that the concentra- tion of metallic catalysts therein was higher than in the monel

1 2 3 4 5 6 7 8 9

Time (hours) Figure 3

heated oil. Thus the acid number curves also tend to show that the relative darkness of oil bodied in the copper kettle is due to the presence of an excess of copper soaps, resulting from the relative solubility of copper in the free acids of linseed oil.

Conclusion

In the production of a kettle-bodied linseed oil, varnish kettles of monel metal have been found superior to copper kettles in two respects: (a) a much paler oil is produced; (b) a lower acid product is formed, because copper is more soluble in the acids of linseed oil than is monel metal.

Large-Scale Preparation of Sodium Amalgam in the Laboratory' By R. R. Read and Carl Lucarini

UNIVERSITY O F VERMONT, BURLINGTON, VI'.

HE usual method of preparing sodium amalgams by the addition of sodium to mercury is a laborious one

and requires the observance of cautione2 In the prepara- tion of small quantities of low-concentration amalgams the expedient3 of melting the sodium under toluene or xylene and adding the mercury slowly suggested the method de- scribed herein for the preparation of amalgams of all con- centrations in quantities of 15 kg. or less.

The top is cut from a steel mercury flask in a lathe and two holes are bored in it. One is tappedfor a length of 6.4-mm. (l/r-inch) pipe, closed a t the lower end, which serves as a thermometer well and stirring rod.

The required amount of sodium is placed in the flask, the top set in place, and 25 cc. of toluene are added through a funnel in the second hole in the top. The flask is then heated until the sodium is melted and the mercury added slowly. During the early stages of the addition there may be bursts of flame, or even slight explosions, but these do not lift the top off the flask. More toluene may be added to prevent oxidation. Some mercury vapor is undoubtedly thrown out of the flask, so that a well ventilated hood is necessary. The latter portions of the mercury may be added rapidly. When the amalgam is completely melted, it is stirred and poured into a round-bottom kettle to cool.

Amalgams up to 3 per cent of sodium may be granulated 1 Received January 28, 1926. 2 A complete melting point curve for sodium amalgams is given by

a Net, Ann. , 380, 307 (1891). Van Stone, Chem. News, 108, 181 (1911).

by vigorous stirring during cooling, the few remaining lumps being crushed with a pestle. This is particularly successful with 2 per cent amalgams. A useful modification is that of pouring the molten material into t ~ l u e n e , ~ but the writers have not found it adaptable to large quantities. To pre- vent ignition, amalgams of 15 to 25 per cent sodium are best poured after the addition of mineral oil. This can be washed off with toluene, care being taken to open up any oil pockets.

The solid amalgam may be crushed in a power-driven jaw crusher or in a large iron mortar by hand. In either case a moist gauze bandage should be worn over the face as the inhalation of the dust may cause pronounced symp- toms of mercury poisoning. The crushed material heats rapidly on exposure and should be covered immediately. One melt, exclusive of crushing, may be completed per hour.

If it is desired to avoid the possible contamination from the iron vessels, smaller quantities of low concentration amal- gam may be prepared in glass.2 As much as 4 kg. of 2 per cent material may be prepared a t once. The sodium is melted down under the toluene on an electric hot plate in a Pyrex beaker, chosen for its unusual thickness and the mer- cury added with caution. The material may solidify. In such a case, after all the mercury has been added the beaker is heated until the toluene has boiled away and the amalgam becomes liquid. The dross is removed and the melt cooled with stirring, the product being finely granular. The time required is about 3.5 hours.

*

Hirschfelder and Hart, THIS JOVRNAL, 12, 499 11920).