1740 Journal of Applied Microscopy 



This silver salt seems to exhibit oblique extinction, probably belongs to the 

 monoclinic system, and may have the formula HAgC4H40e • SHoO. The nor- 

 mal tartrate Ag2C4H40g has been prepared by precipitating silver nitrate with 

 tartaric acid. It is therefore probable that the composition of the precipitate 

 obtained in "Micro " testing will vary according to the reagent used, i. e., tar- 

 taric acid, or primary sodium tartrate, or a mixture of the two. 



Potassium antimonyl tartrate precipitates the compound Ag(SbO)C4H40g •- 

 HgO, at first as an amorphous mass, soon crystallizing in tufts of radiating 

 needles. If the preparation be heated, the precipitate dissolves and on cooling 

 beautiful highly refractive triclinic rhombs separate. It is not always an easy 

 matter to obtain just the right conditions leading to the formation of good crys- 

 tals, 



(See in this connection Barium VI, Journal, 4 : 1327-28.) 



With Potassium Antimonate. 



This reagent applied to neutral solutions in the manner suggested under 

 Sodium (q. v.) yields an amorphous precipitate soon crystallizing in long acicular 

 prisms with bristly edges and showing a decided dendritic tendency. These long 

 needle-like crystals often disintegrate rapidly, leaving only a mass of irregular 

 fragments. Tiny crystallites are also seen in the form of stars and crosses. 

 Occasionally lenticular grains singly and in masses appear. 



This reaction of silver with potassium antimonate is a most instructive one 

 if we recall the fact that in the Periodic System silver falls in Group I under 

 sodium, and should, therefore, behave toward some reagents in a manner analo- 

 gous to the latter. As a further analogy between silver and sodium we have 

 already seen that the normal anhydrous sulphates of the two elements are iso- 

 morphous. 

 Silver Acetate. 



This salt separates from concentrated solutions upon the addition of acetic 

 acid or alkaline acetates, first as a mass of thin plates and thin needles and 

 prisms ; soon large, thin, colorless striated irregular plates are formed. These 

 plates, though irregular, still retain the general outline and proportions of the 

 more perfect plate-like prisms from which they are developed. They extinguish 

 parallel to their length. 



This reaction is an important one, since silver acetate may separate whenever 

 silver is present and an alkaUne acetate is added to mitigate the action of a 

 mineral acid. 

 With Ammoniiun Carbonate. 



Silver carbonate is first precipitated in a fine granular condition ; later, neat, 

 highly refractive crystals of cuboidal aspect, and spherical masses, appear. The 

 reaction is an interesting one and the preparations obtained well worth examina- 

 tion and study. 



Like the precipitation of a number of other silver salts, this reaction is of 

 more importance with reference to the possibility of its interfering with, or 

 obscuring, certain reactions for other elements. E. M. Chamot. 



Cornell University, Department of Chemistry. 



