94 PROCEEDINGS OF THE AMERICAN ACADEMY 



tions ; the obtuse angles on these crystals are often truncated. Less 

 commonly with the characteristic forms just described, long flattened 

 prisms occur, which are terminated by a single plane at a shfrp 

 acute angle, rarely by two. It is easy to see that the rhombic 

 crystals could be formed by the twinning of these prisms. The 

 crystals are very lustrous, of a white color, with a slight greenish 

 cast, and melt at 111° without decomposition. The substance is es- 

 sentially insoluble in cold water, very slightly soluble in hot; soluble 

 in cold alcohol, more so, but still far from freely, in hot. It shows no 

 signs of decomposition when boiled with alcohol. It is more soluble 

 in methyl than in ethyl alcohol, cold or hot ; very freely soluble in ben- 

 zol, chloroform, or acetone ; freely soluble in glacial acetic acid ; solu- 

 ble in ether or carbonic disulphide; nearly, if not quite, insoluble in 

 ligroine. Hot alcohol is the best solvent for it. Strong sulphuric 

 acid has no action on it in the cold, but when hot dissolves a little of 

 the substance after it has melted ; strong hydrochloric acid has no 

 action, hot or cold ; strong nitric acid has no action on it in the cold, 

 but when hot dissolves a little of it, which is deposited on cooling. 

 Neither acid sodic carbonate nor neutral potassic carbonate had any 

 action with it, even in presence of alcohol ; sodic hydrate in aqueous 

 solution was without action ; if alcohol was added, a portion of the 

 substance dissolved slowly with a yellow color, but most of the white 

 crystals were left unattacked ; ammonic hydrate in aqueous solution 

 had no action, with alcohol little or none. The substance behaves, 

 therefore, as we should expect, a salt being formed only by a reagent 

 like sodic hydrate strong enough to remove the NO2 group attached 

 to the side-chain 



The nitrite of bromdinitrophenylmalonic ester is much more stable 

 than the corresponding trinitro compound, since it is not decomposed 

 by boiling with alcohol, or at its melting point, or by boiling with 

 nitric acid ; for, as has been already stated, it could be made by boil- 

 ing for three hours with nitric acid, whereas under these conditions the 

 trinitro compound was converted into the tartronic ester. Nor did 

 longer boiling of the dinitro compound with nitric acid produce the 

 tartronic ester, as even after seven hours it showed the melting 

 point of the unaltered substance 111°. As the trinitro tartronic 

 ester had been obtained also by heating the corresponding nitrite, 

 we tried the same experiment with the dinitro nitrite, and found that, 

 when heated a few degrees above its melting point, it turned rather 

 dark colored, and gave off bubbles of gas, in which bromine was rec- 

 ognized by the smell. The residue was oily, but after solution in 



