Exercise 112. Copper Crystals

Prepare a supply of a dilute solution of sodium silicate (density, 1.06) by dilution of commercial water glass and pour it into an equal volume of 1-normal acetic acid. Add enough copper sulfate to make the solution 0.05-normal with respect to the copper sulfate. Fill several tubes half full of the solution and set them aside until a firm gel is obtained. To each test tube add a layer several centimeters deep of a 1 per cent solution of hydroxylamine hydrochloride. In several weeks, the tetrahedral crystals of copper may be observed, best in bright sunlight. 

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Practice Exercise Copper crystallizes in a face-centered cubic lattice (the Cu atoms are at the lattice points only). If the density of the metal is 8.96 g/cm, what is the unit cell edge length in pm ... 

Additional Exercises Crystals of silver sulfate, silver chromate, calcium tartrate, and copper tartrate. 

Cl pigment blue 15, Cl No. 74160, is an alpha crystal that offers a red shade and the poorest stability of the copper phthalocyanines and as such is referred to as a crystallizing red-shade (CRS) blue. This grade is most often used in rubber and flexible PVC applications. Care must be exercised during the use of PB 15 since this crystal type has poor heat resistance at temperatures above 425°F (218°C) temperatures at which the pigment will likely revert to the more stable, green-shade beta crystal. 

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