1893.] MICROSCOPICAL JOURNAL. 259 



To Mount Certain Salts. 



By NO SIG. 



PARIS. 



1. — SULPHATE OF COPPER AND MAGNKSIA. 



Mr. Thomas Davies in his work " On Mounting Microscopic 

 Objects" ])resent8 with niucli detail tlie means of obtaining pre- 

 jiarations of the donble salt of sulphate ofcopjier and magnesia, 

 which^ if carefully carried out, will give very good slides of this 

 handsome preparation. 



Before commencing to make the slide it is necessary to be 

 assured of the i)erfect cleanliness of the glass; the best we are 

 supplied with here is fluted plate, whicli arrives from Euglarid 

 in half gross packets cut exactly to size 1 inch by 8 and well 

 ground at the edges; these slides are generally quite clean and 

 require no further care; on breathing on each one you can at once 

 see if it is clean enough. Those plates that you do not find 

 quite clean should be put at one side and be soaked in a dish con- 

 taining a small quantity of washing soda, when, in a day or two 

 of time they can be well rinsed in clear water, carefully wiped, 

 aiid then placed in a packet and be wrap})ed up in tissue paper. 



As it is very essential to have clean cloths, they should be 

 washed in a weak solution of soda (no soap used) and well rin- 

 sed in clean wat^r, and rough dried, using a hot iron to flat- 

 ten them, and kept wrapped up in soft paper to keep them free 

 from dust and grease. 



To prepare the solution, mix three parts of a saturated solu- 

 tion of sulphate of copper in distilled water with one part of a 

 saturated solution of sulphate of magnesia, to which add one- 

 tenth part of distilled water and filter. 



Have your hot-plate heated by a spirit lamp ready before- 

 hand, take care that it is pretty level, then select a clean glass 

 slide and place it on the card-board guide marked for the center 

 and drop a little of the solution as nearly in the middle as pos- 

 sible keeping the drop smaller thaa the cover you intend to use 

 in mounting, then place it on the hot-plate until it is evap- 

 orated and keep it there for about ten minutes after it is dry 

 when it looks like a gelatine film with thickened border. Have 

 the microscope read}" with the polarizing apparatus and selenite 

 plate ; when the slide is cool enough to handle, place it on 



