T H E PERIODIDES.
775
resuZts. I need not, however, comnient any further upon Prof. Richard's private letter to Mr. Gladding, since everything of importance in this controversy is settled by an authority which Prof. Richards will certainly approve of; viz., a passage in his own paper in the Zeitschjfffiir a?zorga?zischeChemic, 1895,8,418, which I translate verbatim : ' ' Moreover the observation is of interest, that the error caused by occlusion ordinarily just about compensates that caused by the solubility of the sulphate, so that the final corrected result is almost the same as the real weight. T h e average of the uiicorrected results is 0.3215 in lieu of 0.3214 grani." This, I think, disposes of the aid which Mr. Gladding has solicited from Prof. Richards in his attack upon me. ZURICH, MAS 23, ~Sgj
THE PERIODIDES.' B Y ALRERT
B PRESCOTT.
Recerred Aiig(i5t
T
11,
189j.
HE periodides are remarkable as products of extreme addi-
tive conibiiiation, along with clearly cut crystalline form, distinct physical constants, and instances of rare optical power. They are easily reduced to normal iodides, containing for every atom of iodine firnily bound, one or more iodine atonis loosely bound ; therefore they are often and not iniproperly termed superiodides. Professor Geuther used for theni the terni polyiodide, perhaps by reason of his view that all their iodine atoms are of equal valence in the molecule.' Jorgenson designated theni together as superiodides, though including within their structural type certain double polyiodides not understood to contain additive iodine.J If these coiiipouiids contain, as their behavior has been interpreted to imply, for every atom of iodine that is linked to the base, a iiumber of atoms of iodine linked only to iodine, they offer a striking example of the influence of a basal group upon iodine atoiiis to which it is not linked. T h e one iodine atom that is directly united to the nitrogen or other 1 Read at the meeting of the Aluericarl Association for the Advaucetneul of Science, Spriugfield, Aug. SO, Ihj. 2 A . Geuther, r887' A n n . C ~ P I I(Liebig). I. 140, S z . 8 3f. Jorgensou, 1869 : Ber. d . chem. Ge,., a, 465.
THE PERIODIDES.
777
2, Periodides of ammonium. Periodides of arsonium' and of stibonium if they have been obtained. Periodides of the metallic derivatives of ammonium. T h e same of metallic derivatives of arsonium and of stibonium, if they have been obtained. 3. T h e periodides of organic bases. They are mostly of the quaternary, and the tertiary' bases, of the nitrogen-base family, including bases with oxygen and without it. Phosphonium," arsonium,' and probably stibonium' periodides are known. And, of another type, that of perhalide of a bare aniine base, such as ( R , N ) 12.1, at least triethyl phosphine periodideR and pyridine periodide' have been reported. Also a perhalide taken as pyridine dibromide hydrobroniide .' T h e nitrogen-base periodides belong in two categories, ( I ) those of the alkplanimoniuni bases, and ( 2 ) those of pyridine and its. derivatives. Polyiodides of the vegetable alkaloids belong in the latter division, except the caffeine and theobromine polyiodides. 4. T h e periodide of iodoniuni, the organic iodine base obtained by Victor'Meyer last year.' T h e normal iodide of iodonium is of structural interest to polyiodides generally. 5 . Aroinatic sulphon periodides, as found by Kastle and Hill last year. I" 6. Acid polyiodides, more or less complex, and double base polyiodides, inorganic and organic, including those in which the iodine is not in additive combination, that is, not yielding a distinct part of theiodine to reducing agentswith a goodend reaction. 1 Phosphoniuin not-urai iodide ; I,al)illnrdi6re and Gny 1,ussac: A n n , chirrr. pliys. [z], 6, 304 : A. W. Hofinanii. i S S 7 ; A f r u Clfem. (Liebig), 1 0 3 , 355 ; 1 8 7 3 : Be?'. d. clrciri, GPS., 6, 286. Inflames by contact with iodine. 1111Geuther's table, in 1887, of the periodides then known, t h e only periodides of tertiary bases destitute of o x y g e n which a p p e a r a r e a pyridiue hydrogen pelitiodide. (1,iebig). a n d a quinoline hydrogen tetriodide. both by Dafert ( Geiither : A i f i i . Clf~~rrz. 240, j 4 ) . I n repoitiiig upon these. i n rS83. Dafert says : " S a c h den b i q jetzt hekaiiiiteti Thatsachen schientes. dass n o r tertiare und Arnnioniunibaseii Periodide Iiilden" (Afoirafdr. Cheirt., 4 , 510.) 3 Tetraethylphosphoiiiriiii triiodide, Jiirgeiiseii. A nit. Clrcrri. (Licbig), 140, 74. 1 Tetraalkylarsoiiiiini triiodides, Cahours. isdo : A i i > f .Cheirr, (Liebig), 116, 546: 1S62: ( b i d . 1aa,215. 5 Jorgenson. 1869 : b'cv. d . rhrirr. Grs , 2, 463. 6 Masson and Kirklaud. 1869 : f. Chenr. Soc.. 55, 139. 7 M r . Trowbridge arid tne author in another p a p e r of this date. 8 Griniaux, 1'982 : Compf. t r t r d . , 95, 87 : I?rili. Sac. CJfitn., 30, 127. 9 Brv. d. clieiir. Ges., 17, 1594,1894. 10 Alii, CJiciir.f..16,116. A sulpliur periodide of another order is that obtained in amorphous conditiou by Jorgenseii. 1869 : BCY.d. chem. Ges., 2 , 464.
77s
ALBERT E . PRESCOTT.
Geuther's classification into triiodides, pentaiodides, heptaiodides, and enneaiodides, all with one atoni of iodine firmly bound,' was of service in his own study of structural features. But Geuther admitted a category of sesqui-, di-, tetra-. and liesaiodides. There is surely a prevailing proportion of m a numbers of a d d i f k e iodine atoms, making odd numbers of f o f n l atoilis of iodine, per molecule " of the periodide. Generally this is an assumed " molecule'' of nionobasal proportions. That two or more monovalent groups of the aniiiioniuni type should enter into the formation of a periodide molecule, in some cases, is theoretically probable, to sap the least. if periodides are individualized in niolecules at all. T h e hypothesis of Jorgenson in 1869,' providing for both iiioiiaiiiiiioiiiuiii and diamnioniuin types of periodides, is not an unreasonable one. Moreover, there is to be considered the probable occurrence of an iodine atoni in the fourth position of the organic ammonium group, phosphonium group, etc., with whatever degree of firmness of binding may be determined for it i n this position. T a k e it all in all, therefore, it seems to nie that at present we know no law of even or uneven numbers of iodine atonis in superiodides, either to help or to hinder our interpretation of results. With evidence of molecular weight we may gain approach to such a law. In division 6 of the classification above there are without doubt included certain strictly normal iodides. T h e iodomercurates a s strongly marked double iodides, and the Herapathites a s representative acid superiodides come in this division. An interest in the iodomercurates of the nitrogenous bases3 has been but one among several causes contributing to n;y own interest in this subject a t present. But I have not yet made such a n inquiry irito the action of deiodinizing agents upon the known double iodides as might reveal what superiodides there are among them. Some of the tabulations of the super-iodine in double inorganic polyiodides given by GeLtther4 seem to invite further inquiry. T h e acid periodides in many cases undenia(1,iebig). 140, 74, So. 2894. d . c h r m . Ges.. a, 465. 2865. S Anz. Chem.J.. 1 4 . 607, 1892 ; a. 294.1880. 1 A n u C7trsi.
2 Brv. 4
A n n . (%em. (Liebig), 240> 81.
P h a w r . Rund.,
11,
146.
THE PERIODIDES.
779
bly contain additive iodine, but the question of their constitution, like that of mixed halides in general’ is more complicated and is perhaps of less special significance, than that of the simple polyiodides. With the exception, then, of the metallic, the iodonium and the sulphon periodides, the formation of superiodides is limited, so far as I have found, to compounds of the nitrogen family of elements. T h e first periodide recognized, so far as I find record, may have been that of ammonium, termed by Berzelius the biniodide. After the discovery of iodine the first workers upon the alkaloids seem to have mistaken, in some instances, a produced periodide for a mixed excess of iodine to be taken up by more alkaloid in preparation of the hydriodides.* In I839 B ~ u c h a r d a ta, ~medical writer in Paris, recounts that, when dogs were being surreptitiously poisoned with strychnine in Paris, and an antidote was asked for, first Guibourt recommended powdered galls, and then Donne advised iodine tincture,’ whereupon Bouchardat himself, approving the use of iodine, said they should use it in potassium iodide solution. H e then set forth some interesting characters of the alkaloid periodides, comparing them with aiiinionium periodide, quoting for this the name froy Berzelius mentioned above. De Vrij has said that Bouchardat anticipated Herapatli in production of iodosulphates. A modest nienioir of Donne, in connection with the Parisian interest just referred to, upon the use of iodine as an analytical reagent for vegetable bases, was referred for criticism to D’Arcet and Chevreul, who made quite an elaborate report’ upon the action of free chlorine, bromine, and iodine, in intensive application, with admonition as to undue dependance upon any single analytical reactions. In 1846, in his suniinary of ‘the distinguishing reactions of the more importaut 1 T h e Chloriodides of Organic Bases, and Pyridine Chloriodide, Pictet and Krafft, 1892 : Rull. Soc. Chim.[3], 7,72. ZPelletier and Caventon, 1819. A n n . chim. phys. [ z ] IO, 142; A n n . der Phys. Gilberf, 63,306. 8 Bouchardat, 1839 : Cotnpf. rend. g, 475 ; L’fnstilul. 7, 358. 4 Both apparently actingunder the opinioti, due to that little chemistry which has often brought all chemistryinto disrepute, that a precipitant in a test-glass will serve a s an antidote in the stomach. b A n n . chi?n.phys. [ z ] 38, 8 2 .
780
THE P E R I O D I D E S .
alkaloids,' v. Planta-Richenau specifies for each a precipitation by free iodine. I n 1Sj4, shortly after A . 1%'. Hoftnann'sfaiiious elucidation of organic ammonium bases,' Weltzien contributed a full and careful description3 of the tetramethyl and tetraethyl amnionium triiodides. I n 1858 Muller added a good account4 of quaternary mixed alkyl ammonium triiodides. I n I 866 IVagner' proposed iodine precipitation and a method of treatment of the periodide precipitates for separation of alkaloids from estract i w matters. Arid Tilden made a contribution in 1 5 6 6 . ~ T h e masterly work of Jorgensen, beginning with his dissertation at Copenhagen in 1869, continuing for about nine >.ears' in this field, and extending over riearlj. all relatioils of polyiodides in general, have had the respect of all ciieiiiists, wliik hardly yet fully assimilated. In 1887 this subject was taken up by Professor :I. Geutlier, a t Jena, \\ho contributedt a good number of new periodides from his own laboratory. with a tabulation of all then obtained, and a vigorous and independent study of the features of structure. T h e crystallographic investigations were made by Prof. Ludecke. Prof. Geuther died in 1889. In 1869 Jorgenseiig foriiiulated his idea of the probable structure of "these compounds," taking iodine as trivalent, as follO\VS : "'
1.1 K , S . I : 1 : R , S . I : . .. I 1.1 numbers of iodine atoms.
;
etc., for periodides of urieveii
?'
R,?;.I: 1' 1 : I . N R , for those of even iodine numbers. I . 1.1 And R , N . I :
I : H g for a typical iodomercurate. This simple I
dissertation, 1846. A n x . Chem. Phnvm.. 7 4 , 245. Phil. Trans. I. 93-13', 357-398. 3 A n n . Chon. P h a r m . , 91, 33: gg, I. 4 i l f r n . Ciirnr. Phnrm.. 108,I . 6 Z f x h ) , .anal. Chem.. 4 , 387. 0-L CJiem. Soc., 19, 145,187,. 7 / . p r . a k f . CJiem., 18;0-;8, [ z ] 1 , 347, 433; 3, 145. 328; 1 4 ~213, 356; 15, 65. 418; 16, 3 2 . B w . d . cheni. Ges.. a , 460, 1869. 8 A fin. ('hpm. (1,iebig). 040, *I. 9 Rev. d . diem. Ges., a, 465* 1869. 10The present writer gives R,N as ail expression for any orgauic base of nitrogen, instead of '' Alk" used by Jorgensen. 1 Heidelberg
?.1-95o-.c I
.
AN IMPROVED GAS REGULATOR.
7 8I
conception is, of course, consistent with an iodine valence of five or of seven. Geuther' drew from the optical studies of the color of iodine crystals by Conroy the indication that the molecular mass of the crystalline element is that of (I,)". H e made this generalization as to color of the periodides, that the tri and hepta iodides were red-brown to violet-blue, and the penta- and enneaiodides green to green-black, the higher iodine numbers giving the deeper shades.$ H e presents structural schemes of orders as follows : For the triiodides, ( RJ,) I,, = 6 (R1.1,) ; for the haptaiodides, (R,II) I,, = 2 ( R1.1,) ; for the pentaiodides, (R,I,) I,,= 4(I
