400 
ELEMENTARY CHEMICAL MICROSCOPY 
chlorides are obtained with the chlorides of Al, Cr, Ba, Sr, Ca, 
K, Na, Lid 
The cesium chloride test is made more satisfactory and much 
more sensitive by obtaining an iodo-salt instead of that described 
above. This is accomplished by adding a fragment of potassium 
iodide to the test drop after applying the cesium chloride. Crys¬ 
tals of a double iodide of cesium and antimony having the same 
form as the double chloride are obtained but they are deep orange 
yellow or orange red instead of colorless. The composition of 
these crystals is not well established, but the weight of evidence 
seems to be that three molecules of Csl unite with two or three 
molecules of SbL, rather than with SbL- 
The test thus performed is an excellent one, but requires con¬ 
siderable experience in order to properly control the conditions. 
The test drop must be neither dilute nor concentrated and only 
just sufficient hydrochloric acid should be present to prevent an 
antimonyl compound from forming. It is also better to adopt 
for this iodide modification the method of applying the reagents 
suggested by Schoorl,^ namely adding a fragment of cesium 
chloride to one side of the drop and a fragment of potassium 
iodide to the opposite side. 
The double iodide of bismuth separates in rhombs and elon¬ 
gated hexagons, rarely in the regularly formed hexagons of the 
antimony salt. Their color is a deeper orange (or even a red) 
than that of the antimony double iodide. 
Tin forms yellow cesium iodostannate in regular octahedra. 
Precautions. 
When iodine separates it is an indication that too small an 
amount of potassium iodide is present. 
In the event of a precipitate resulting upon the addition of 
hydrochloric acid at the beginning (Ag, Pb, Hg, Cu) sufficient 
acid should be added to complete the reaction. Decantation or 
filtration should then be resorted to and the clear solution care¬ 
fully concentrated to remove the excess of acid until a drop of 
* Vermande: Pharm. Weekblad, 66 (1918), 1131. 
* Beitrage z. mikrochem. Anal. Wiesbaden 1909, p. 49. 
