hostetter: apparatus for growing crystals 87 



To the essential conditions previously discussed we must 

 add another if the crystal-growing process is to be continuous; 

 namely, that the supersaturated solution must be given definite 

 circulation over the nuclei to be developed. Recently a crystal- 

 growing apparatus with controlled circulation has been patented 

 by Kriiger and Finke.^ In this apparatus the mother-liquor 

 is saturated in one chamber and then passed into another chamber 

 of lower temperature where deposition takes place on the crystal 

 nuclei to be grown ; the solution is then returned to the saturating 

 vessel. This patent of Kriiger and Finke furnished the basis 

 for the apparatus described by Valeton® and the apparatus de- 

 scribed below has been taken in part from that described by 

 these investigators, but with numerous changes in details of 

 construction. 



Essentially the apparatus consists of 2 thermostats (S and C 

 in figures i and 2), connected by tubes, with the necessary 

 stirring and circulating devices. The thermostats are filled 

 with saturated solution of the crystals being studied. One 

 thermostat — the "saturator" (S) — contains the crystals, which 

 maintain the solution saturated; the other thermostat — the 

 "crystallizer" (C) — is held at a slightly lower temperature 

 and it is in this cell that growth takes place. The thermostat 

 vessels are storage battery jars, 20 by 20 by 20 cm., with 25 

 mm. holes drilled through the sides where necessary for the 

 entrance of tubes. The thermoregulators^ (shown at T and Ti) 

 are filled with mercury, and operate, through relays, the 5 -candle- 

 power cylindrical carbon lamps (H and Hi) used as heaters. 

 In the saturator the cooled solution stream flows oyer a heater 



* German patent No. 228246, a copy of which I have been unable to secure. 

 A brief description of their apparatus is given in W. VoigT. Lehrbuch der Kristall- 

 physik, p. 9, 1910. 



^ J. J. P. Valeton. Ber. Sachs. Ges. Wiss. 67: 1-59. 1915. 



' Attention may be here called to the threaded glass parts of the thermoregu- 

 lators which carry the adjustable contacts. These threaded parts are small homeo- 

 pathic vials (Whitall Tatum Co.) which have been drawn down and sealed to 

 ordinary soft tubing. I have found their use advantageous in other cases where 

 glass-to-metal connections are necessary. 



