ANALYTICAL EDITION
June, 1944
Table 111.
Concentrating Effect Caused b y Removal of Liquid from an Aerosol Bomb
(Containing originally 400 grams of a 5 % solution of cottonseed uii in Freon-12) S o l u t i o n Withdrawn Relative Concentration of Oil ' i hy weight Determined Calculated 0 20
80 90
100 9,
51
70
(100 0 )
100.0 102.1 105,2
101.5. a v .
101 2 105.3, 106.5. av. 105 9 108.9, 109.1, av. 109 0
108.0
heed oil W a 6 chosen instead of sesame oil because it did not oxidize when heated for the analyses. The initial concentration wau determined by withdrawing two 5-gram samples into pressurr test tubes, which were w-righed before and aftvr to .determine the exact weight, of the samples. The apparatus was used n-ithout the hydrometer. The volnt,ile solvent was then allowed to evaporate, and the test tube contmning thc residue was removed from the frame and heated for 30 niinutcJs :it 110' C. The weight of the residue wa? then dett!rrnined and the concentration by weight of nonvolatile matter calculated. Duplicate samples n-ere also taken aftrr 50, 80, and 90% of the solution had been allowed to escapc. 1Iechxnird difficulties made the results unreliable after 95% had h e w removed. All operations were ciirried out nt 80" F. Tht. r(wi1ts :we sho~vnin Table 111. The degree of concordance shown is good, considering the experimental difficnltirs involved. The over-a11 effect is compara-
A
357
tively small until the container is alrnost empty and, sincr, i t is in the direct,ion leading to greater assurance of getting the required minimum concentration, not very important in the actual application of the insecticide. I t might be important, however, to a manufacturer filling small containers from a large one. The last containers to be filled will contain more insecticide than the first unless some compensatory measures are taken. I t is also important when samples of solution are being used for test purposes as a standard of comparison. I n precise laboratory tests it would be good practice to use not more than 50% of the original solution. The simplest procedure in the commercial filling of :ierosol containers is to add sufficient pure Freon to the reservoir at, intervals to maintain approximately the original concentration. This procedure is used by some present aerosol manufacturers. Although the foregoing discussion has been based wholly on data pertaining to dichlorodifluoromethane, the formula developed will obviously apply to all liquefied-gas solutions for which the densities of the liquid and gaseous phascs rrmnin reasonably constant during evaporation. LITERATURE CITED
(1) Bichowsky, F. R., and Gilkey, IF'. K.. IND. ENG.CHEM.,23, 366
(1931). (2) Buffington, R. M., and Gilkey, W. K., Ibid., 23, 254 (1931). (3) Goodhue. L. D.. Ihid., 34, 1456 (1942).
Modified Bailey Buret
L O R E N H A M M A C K AND CHESTER L. N A E G E L I N ' Chemical Laboratory, San Antonio A S F Depot, Grayson Street Station, San Antonio 8, Texas
T
HE Sail Antonio Army Service Forces Depot Laboratory has, for some time, been analyzing large numbers of samples of mayonnaise and other semiyolid salad dressings. Tests have been made according to the methods of the Association of Official Agricultural Chenikts ( I ) . IVeighing out such samples n i t h the Bailey weighing buret ( 2 ) ctoiy. The only size available to the has never proved sat aut,hors has been the 30-m1. capacity ~i-liichholds an insufficient quantity of salad dressing if duplicate determinations are to he made. Salad dressings, moreover, are of such consistency that there is almost no flon. of material from the tip of the buret due to gravity alone. Forcing the sample out with t,lie plunger is a very .;low process and results in the accumulation of a considerable quantity of material on the adapter and on that portion of the plug which projects above. Such a sitiiation inevitably results in 1 0 ~ s . A fairly *iniple modification of the Bailey buret was decided upon as tlie best solution of this problem. The changes involved mere enlarging t,he buret to a capacity of 100 ml., straightening out t.he top of the buret completely, eliminating the constriction, and adding a plunger to go down inside tlie buret and around the plug. A11 clearances were kept to a minimum. Buret d is constructed from 51-mm. Pyrex glass tubing with joint a t top and inside 15/20 and outside outside 50/12 10/18 joint at. the constricted bottom. Distance between upper joint, and beginning of constriction is 50 mm. Flask B has outside l5j20 -$- joint and over-all diameter of 67 mm. Plug C is a 6-mm. glass rod. 165 mm. in length - .(over-all). and contains inside 10/18-$- joint. Plunger D is of 18-8 8-mm. (l/az-inch) stainless steel, consisting of a tube and disk mot-welded together. Inside diameter of tube and diameter of dihk are of sizg to give snug fitting around plug :tnd invide buret. respectively. Adapter c,r stopper E i+ hollow-ground and has inside j0/12 joint and orifice to fit over tube D. The modified buret is filled while sitting on the fla\k base B, with plug C in place. Plunger D is then fitted around the plug I
1
,
Present address, San Antonio Bir Depot, Kelly Field, Texas.
and allowed to rest on the materitil
The adapter, E , is finally placed in position, and the assembly is weighed. To remove the sample, the plug is raised and held in open position and: Kith the same hand, the plunger is pressed downward; forcing out the material. When enough sample has been taken, the plug is pushed into the joint, pressing out the last drop before the buret is returned to the flask. I t is immediately apparent that the total weight of t,he assembly, filled, is too great for the capacity of an ordinary analytical balance. The assumption is that the larger samples are to be weighed on a more rugged balance, an accuracy of 0.1 or a t most, 0.01 gram being adequate. The modifiedBailey buret should find use in analyzing samples, such as soft grease, paste paints, cert,ain asDhalts, water-reDellent emulsions, and other semisolid materials. The plunger, too, can always be removed and the buret can be used to an atlvantage for any bulky sample. Satisfactory working models ot this buret were obtained from the Scientific Glass Company, Bloomfield, S.J., and have been in rontinuous use with marked success during the past year. Steps are now being taken to remove minor defects in the design. LITERATURE CITED
(1) Assoc. Official Agr. Chem., Official and Tentative Methods of Analysis, pp. 475-7 (1940). (2) Bailey, H. S., J. IND. ENG.CREM.,6, 941 (1914).
