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508 THE PHOTOGRAPHIC NEWS. weights and measures sanctioned by the last Convention. If we insist on the adoption of the system that is palpably inferior to the generally used metrical, we shall be put at great disad vantage at the Congress. The same is to be said respecting a system of weights and measures proposed elsewhere, recom mending us to express our formul in parts. I shall put as an instance, how can you answer a question, “How much emulsion have you to use to cover a sheet of paper of certain size, using parts as measures ? ” Photography, like all other sciences, is not national, but belongs to all humanity; therefore, we must use terms that can be intelligible to all humanity, and that is the object of the Congress. The metrical system is that universally intelligible expression of weight and measures. Mr. Haddon mentioned that a deputation had been appointed by the Photographic Society to attend the Brussels Congress to support the suggestions adopted by them. The report was subsequently adopted with about one dissentient, and a hearty vote of thanks was accorded to Mr. Haddon for the trouble he had taken in the matter. On Friday the members of the Convention divided their attention between Glastonbury and Wells, and Corsham and Lacock Abbey, privileges being afforded at each place for obtaining views, while at Lacock Abbey the additional advantage was obtained of inspecting the examples of early photographic art produced by Fox Talbot, dating from 1834 downwards. In the evening the Photographic Convention of 1891 was brought to a successful close in true English fashion by a dinner and smoking concert. All the arrangements of the week were carried out in a very complete manner, and we must congratulate Mr. Briginshaw, the energetic hon. secretary, on his talents as a successful organiser. SOME NEW ADDITION COMPOUNDS OF "THIO- CARBAMIDE ” WHICH AFFORD EVIDENCE OF ITS CONSTITUTION* BY J. EMERSON REYNOLDS, M.D., F.R.S., PROFESSOR OF CHEMISTRY, UNIVERSITY OF DUBLIN. D.— Compounds of Thiooarbamide with partially substituted Alkylammonium Salts. The strongly contrasted results afforded by ammonium and by tetrethylammonium salts invested with much interest the examination of any compounds that could be formed by the union of thiocarbamide with partially sub stituted alkylammonium salts. The products first obtained by the union of thio carbamide with primary, secondary, and tertiary ammo nium salts appeared to resemble those prepared with the simple ammoniacal haloid salts as described in A, that is to say, they seemed to be compounds of the tetrathio- carbamidammonium type. But the analytical data obtained with those products were not satisfactory; hence, as soon as time permitted, the work was repeated very carefully, with the results stated below. The alkylammonium salts used at first were purchased, but those subsequently employed were prepared in my laboratory by the direct action of the required acid on the pure amine, so that ordinary ammoniacal salts were excluded. I shall first describe the results obtained with the diethyl compound ; the chief interest attaches to it as being intermediate between ammonium bromide on the one hand, and tetralkylic bromide on the other. A compound of diethylammonium bromide with thio- carbamide was formed when 3'8 grams of the bromide in * Continued from page 485. absolute alcohol was boiled with a similar solution of 7’6 grams of thiocarbamide. On cooling, a crop of crystals was obtained which was evidently a mixture of thiocarbamide and a new compound, and contained only 12’08 per cent, of Br, but 31-53 per cent, of S; whilst its melting point was not sharp, liquefaction commenced at 135°, and was not complete under 145°. The mother liquor, when concentrated, afforded groups of fine, thin prisms, resembling somewhat the ammonium bromide compound in its mode of separation. These crystals were drained, slightly washed with absolute alcohol, and recrystallised from the same solvent. The melting point of this compound was sharp between 133° and 134°. Some months afterwards this preparation was recrystallised and was found to have the same melting point. It was observed that crystals began to form in the liquid at 174°. A complete analysis was made, with the following results:— I. 0'3575 gram gave 0’2075 H,0 and 0-2891 CO,. II. 0-181 „ 39-3 c.c. of N at 14° and 755 mm. III. 0’228 „ 0-427 BaSO 4 . IV. 0’272 „ 0'131 AgBr. The formula (H 4 N s CS) 3 H 3 (C a H 5 ) a NBr requires:— Theory. Found. C ... ... ■ 21-99 per cent. 22'05 per cent. H 6-28 „ 6'44 N 25'65 „ 25'23 „ S 2514 „ 25-74 „ Br 20'94 „ 20'49 „ 100'00 It is to be noted that this compound is very sensitive to the action of water; anhydrous alcohol must be used in its preparation, and if that used for recrystallisation be much hydrated, a mixed product is obtained which contains free amide and, possibly, a dithiocarbamide com pound. Hence great care is required both in the prepara tion and purification of the trithiocarbamidediethyl- ammonium bromide. I have not succeeded in preparing a tetrathiocarbamide diethylammonium bromide ; if it exists in solution, it is certainly decomposed when crystallisation takes place, even from anhydrous alcohol. At the time my former paper was written (Zoc. eft.), only a rapidly crystallised product, from a concentrated solution, had been obtained, and the bromine in that product was found to be near to the percentage required for a tetra-compound, but I am not satisfied that the material then obtained was homogeneous. Diethylammonium chloride also unites with thiocar bamide and affords a silky mass, which, however, always contains some free thiocarbamide. The best product melted about 136°, but not sharply ; and, like the bromide, when heated to 175° crystals began to form in the molten substance and increased in amount until the whole became nearly solid at 180°. This somewhat impure material afforded 10-14 per cent, of Cl and 29-90 per cent, of S. A trithiocarbamide compound requires 10-51 per cent, of Cl and 29 -95 cent, of S, while one containing 4 mols. of thiocarbamide requires 8-6 per cent, of Cl and 31 percent, of S. The latter is, therefore, excluded; hence the crystalline substance examined contains a sensible propor tion of free amide adherent to the chloride of trithio carbamidediethylammonium, analogous to the bromide already described. Triethylammonium Bromide Compounds with Thio-