Mr. Graham's Account of the Formation of Alcoates. 271 



obtained from the slow crystallization of comparatively weak 

 solutions ; but in solutions which have been fully saturated, or 

 nearly so, at the boiling temperature. In the" former case, the 

 crystalline plates are large, but confused, and nothing but an- 

 gles can be made out ; while in the latter, the forms, under 

 which the plates appear on the surface of the solution, and to 

 the greater advantage, on the sides of the vessel, are generally 

 distinct. These plates are always small, often beautiful, and 

 delicately striated ; and they always present the form of isos- 

 celes triangles. In general, four of these triangular figures are 

 grouped with their apices together ; and if similar, they form 

 a square. But, as more frequently happens, the opposite pairs 

 of triangles only are similar ; and the figure presented is a 

 rectangular parallelogram, divided by two diagonal lines into 

 four triangles. The resolution of the rectangle into triangular 

 figures is rendered perceptible by the discontinuance of the 

 striae, and the formation of clear diagonal lines, which have 

 a beautiful effect. These crystals cannot be removed from 

 the phial in which they are formed without injury, from their 

 softness. Exposed to the air, they speedily deliquesce from the 

 absorption of hygrometric moisture. The heat of the hand is 

 sufficient to melt them. The whole of the alcohol is expelled 

 by a heat amounting to 250°, and pure chloride of calcium 

 remains, which emits nothing else upon being heated to red- 

 ness. 



A quantity of this alcoate was dried, first by strong pressure 

 between many folds of linen, and then by pressure between 

 folds of blotting paper. The alcoate, carefully dried in this 

 way, had a white appearance much resembling bleached wax, 

 and was soft, but without tenacity. 



Ten grains were heated in a glass capsule, till the whole of 

 the alcohol was driven off. There remained 4*1 grains chlo- 

 ride of calcium. The atomic weight of chloride of calcium is 

 7, and that of alcohol 2*875. In the alcoate, 4*1 grains chlo- 

 ride of calcium were combined with 5*9 grains alcohol. 



4-1: 5-9:: 7: 10-0731. 



In a second analysis, in which 20 grains of alcoate were em- 

 ployed, the result was precisely similar, as 8*2 grains chloride 

 of calcium remained, which is just double what was obtained 

 in the previous case from half the quantity of alcoate. If this 

 alcoate should be considered a compound of one equivalent 

 proportion of chloride of calcium, and three and a half pro- 

 portions alcohol, the alcohol would amount to 10*0625, which 

 approaches very nearly to the experimental results. But it 



would 



