Lab Partner: Wilbur Tux
TA: Chuck Root
January 1, 1900
In this lab, the well-known alchemist's technique for turning common lead into gold will be explored. This conversion is important for several reasons: it supplies a almost free source of gold, it appeases the demands of kings on their court alchemists, and most importantly, it teaches one new (rather, old) techniques invaluable in the chemistry laboratory. The properties of the resultant gold are analyzed to see the efficiency of the procedure.
A chunk of lead was acquired from stock. The lead was placed in a beaker, and two pinches of magic powder was carefully sprinkled on top. Only one pinch was called for in the lab, but I wanted to be sure I got a good yield, and given that magic powder has no mass, and a pinch depends quite heavily on the size of one's fingers, this increase seemed justified. No change appeared after several moments of waiting. Upon consulting with the
idiotichelpful TA, it was realized that the incantations were never said. In a medium voice, with strict pronunciation (classical Latin form), "plumbum ad aurum" was chanted.
Water was put in a 100ml graduated cylinder. The gold was carefully dropped into the graduated cylinder so that it rolled down the side. This way it wouldn't splash the water, or hit the bottom too hard and break the graduated cylinder.
A small sliver of this material was cut off with a knife (this was easy because of its ductility). It was placed in a 100ml Erlenmeyer flask. 25ml of aqua regia (HNO3 and HCl) was measured out in the fume hood, and added to the flask, still in the fume hood.
After the bubbling stopped, some of the green solution was poured into a cuvet so that it was filled 2/3 of the way to the top. Another cuvet was carefully filled 2/3 with stock gold chloride solution. A third cuvet was filled with distilled water. The cuvets were brought to the UV-VIS. Using the distilled water as a blank, spectra were taken of the two solutions.
Initial mass of lead: 134.23+/-0.05g
Observations: It was dull grey in color, and soft and ductile in texture.
Mass of the new substance:224.54+/-0.05g
Observations:The lead immediately started changing to a golden color, and the magic dust started glowing bright green. After the incantation was said three times, a bright green flash came from the beaker, and all glowing stopped. The lead was now gold in color, but appeared to have the same properties of being dull in its goldness, and soft and ductile still.
Table 1: Density of the New Material
Initial Volume of water 50.25+/-0.02ml Final volume of water 61.95+/-0.02ml Volume of new material 11.70+/-0.02ml Density of new material 224.54g/11.70ml=19.17g/ml
The propagated error is +/-sqrt(0.052+0.022)=+/-0.054g/ml.
5.02+/-0.05g of new material was reacted with aqua regia. An orange-brown gas evolved with lots of bubbling. The solution turned dark green with a tint of brown. Upon carefully smelling the gas, it was found to be quite unpleasant.
Table 2: UV-vis Data
green solution: foo.dat
stock gold solution: bar.dat
The spectra were rather similar, and gave the similar peaks near 378nm and 684nm
The first thing to be noted is that mass was not conserved in this reaction. It started with about 134g of lead, 0g of magic powder (remember, magic powder doesn't have mass), and ended with over 224g of mass. While this goes against what is being taught in lecture, magic dust tends to have properties that defy scientific investigation, so the breaking of this fundamental law is not surprising. The density of the new material is 19.17g/ml. The correct density of gold is 19.3g/ml, so we aren't quite within estimated error, but that could be due to incomplete conversion of lead into gold. Lead has a density of 11.35g/ml, so we know that the material is not lead. Comparison of the spectra confirms that what we have is gold. Some sources of error would include small air bubbles accompanying the gold when finding the volume. The density of gold is also only given with 3 significant figures, so that could be a source of error. It appears that two pinches of magic powder was plenty to bring the conversion to near completion. After conferring with other students, it was found that one pinch was plenty, and even less worked fine. It is hypothesized, then that the magic powder acts as a catalyst in the conversion from lead to gold.
Back to ICN Labs