''m feature I CHEMICAL PROJECTS

Research Ideas for Young Chemists Compiled by JAY A. YOUNG, Kings College, Wilkes-Barre, Penna. I JOHN K. TAYLOR, National Bureau of Standards, Washington, D. C.

Solubility of Sulfur: An Undergraduate Research Project SeeBnoos~, M., J. Chem. Edue., 28,434435 (1951).

The solubility of sulfur in volatile solvents is determined by For precise work the solute and solvent selected should he placing an excess of sulfur in the selected solvent in a flask fitted known to he pum. Prepare pure solute and solvent, check their with a reflux condenser. At various selected temperatures, after purity by suitable analytical techniques, and measure the soln- equilibrium has been established, aliquots are withdrawn and bility characteristics of this solute-solvent pair. weighed, the solvent evaporated, and the residual sulfur weighed. In comparison with the total possible number of solute-solvent For nan-volatile solvents, a weighed quantity of sulfur is placed pairs, data an solnhilities in the published literature are quite in a weighed quantity of solvent and the temperature raised until incomplete. Aftcr a thorough search of the literature, select a all the sulfur is dissolved. The temperature at which the mixture solute-solvent pair for whieh there are no data or for which the becomes turbid, as the solution is cooled, is noted. data are incomplete and determine the soluhility characteristics

of this new solutesolvent pair. Materidle of analytically de- Questions: termined purity should be used and tho necessary technique

should be acquired by performing the appropriate operations The procedure described in this article can be used for many with a solutesolvent pair whose solubility characteristics are

soluteaolvcnt systems. Select any solute and solvent and dcter- known, repeating until your data. conform with those in the liter- mine the solubility of the solute in the solvent as a funotion of ature, before proceeding to the new pair. Any literature search temperature. Is there any relationship between the solubilities of toidentify gaps in the published literature could begin, but should a selected solute in a series of homologously or isomerieally re- not end, with Chemical Abslraets. Precise data on new solute litted solvents? solvent pairs might well bc publishable.

Daerrnination of the Density of Oxygen Gas See REHERS, B. A,, J . Chem.Educ., 31,139-140 (1954).

Oxygen, supplied from a pre-weighed "Oxybomb," is collected over wrtter. The volume, pressure and temperature of the col- lected gas are measured. These data, together with the weight of the partially exhausted Oxybomb, can be used to calculate the density of oxygen under the pressure and temperature a t which i t was collected. (An Oxybomb is a small 2.5 in. X 0.62 in. cylindrical metal cartridge filled with oxygen under pressure. A needle valve whieh fits the neck of the cartridee is used to control the amount of gas removed from the cartridge.)

Cartridges of other gases are available, although special needle

valves not commercially available would have to be designed and constructed for some of these.

Questions: What is the molecular weight of oxygen? Using oxygen, evaluate R, the ideal gas constant. Haw many molecules are there in one mole of oxygen? Determine the molecular weight of a gas other than oxygen. Using a gas other than oxygen, determine the value of R or of

Avogadro's number.

Molecular Association Equilibria from Distribution and Related Measurements See D ~ m s , M., AND HALLAM, H. E., J. Chem. Edue., 33,322-7 (1956).

Many compounds are soluble in more than one solvent. For example, acetic acid is soluble in water, in benzene, and in other liquids. If an aqueous solution of acetic acid is plaoed in a vessel containing same benzene, the sretic acid dissolves, to some extent, in the benzene. After a suitable period of time, an equilibrium is established between the acetic acid in the water layer and in the benzene layer:

H0Aci.w.. s HOAci.b,,.,..

The data are obtained by adding benmne to an aqueous eolu- tion of acetic acid and mixing vigorously. After the layers have separated upon standing, aliquots of both layers are titrated with s. base of known concentration. (Details can be found in any laboratory manual of physical chemistry. The liquids should he at a known, constant temperature, and should be maintained at this temoerature until the aliouots are withdrawn.)

The above equation is incomplete in that i t does not indicate the ionization of acetic acid in wrtter solution, nor does it indicate the molecular associatian of this sohte in benzene. This equa- Is acetic acid dimerio in benzene. ar does it exist in some other tion is closer to the truth: form in this solvent?

2H80t + 20Ac- + ZHOAei.,t,, (HOAC)~~,~,,~ In what form doea acetamide exist in chloroform solution? Using other solutes and solvents, determine the degree d

However, data obtained from laboratory experiments indicate association of the chosen solute in the selected solvent. that this equation, also, is not completely accurate, particularly (This investigation is pa7tialarly suzlable jm the student who is with respect to the species which exist in the brnaene ~olution. interested in the relatianship belwea mathematics and chemistry.)

Volume 38, Number 5, May 1961 / A353