ON THE 
 
 FLUORINE COMPOUNDS 
 
 OF 
 
 URANIUM. 
 
 INAUGURAL DISSERTATION 
 
 FOR 
 
 THE DEGREE OF DOCTOR OF PHILOSOPHY 
 
 ADDRESSED TO 
 
 THE PHILOSOPHICAL FACULTY 
 OF THE 
 
 UNIVERSITY OF GOETTINGEN 
 
 BY 
 
 H. CARRINGTON BOLTON 
 
 OF NEW YORK. 
 
 BERLIN. 
 
 PRINTED BY UNGER BROTHERS, PRINTERS TO HIS MAJESTY. 
 
 1866. 
 
3b lo 
 
 
 
 
 
 
PREFACE. 
 
 The following researches were begun in the Laboratory 
 of the University of Gottingen at the suggestion and under 
 the direction of Professor Wohler, to whom I here ex- 
 * press my heartfelt thanks for the great kindness and un- 
 remitting attention conferred upon me during my resi- 
 - dence in Gottingen. The investigations were completed 
 in the University Laboratory at Berlin under Professor 
 Hofmann, to whom I also acknowledge my indebtedness. 
 
 My sincere thanks are due to Drs. R. Fittig and 
 C. A. Marti us the gentlemenly and able assistants in 
 the respective Laboratories, for their kind assistance in 
 this work. 
 
 Berlin. January 28th 1866. 
 
 
 p. 37443 
 
NOTE. 
 
 Within a very few years the attention of chemists has 
 been directed to the quantivalence (or atomicity) of the 
 elements, which has given rise to new theoretical specu- 
 lations respecting the constitution of chemical bodies. So 
 new are these theories however, that not a few elements 
 remain to which they are still to be applied. Thus it 
 happens that no chemist who has studied uranium and its 
 compounds, and none of the literature whether in textbooks, 
 monographs or dictionaries, treats this subject in the light 
 of these modern theories. 
 
 In this dissertation therefore the formulae being new, 
 and these necessitating the employment of new names, 
 I have added the old names throughout and occasionally 
 the old formulae; giving to the latter however a subordi- 
 nate place corresponding to their importance. 
 
 Our present knowledge of the uranium compounds is 
 too limited to allow us to establish with any degree of 
 certainty the quantivalence of this metal; but the facts 
 warrant the doubling of the old atomic weight as given 
 by Peligot, and it is taken in the following pages as 
 equal to (2x60 =) 120. Should a compound of uranium 
 be hereafter discovered which is sufficiently volatile to 
 admit of determining its vapor-density, and this is by no 
 means improbable, then the true quantivalence of the ele- 
 ment can be firmly established. 
 
INTRODUCTION. 
 
 In the year 1789, Klaproth 1 discovered in pitch- 
 blende a peculiar metallic oxide to which he gave the 
 name uranium. Richter, 2 Bucholz, 3 Lecanu 4 and 
 Brande 5 were among the first to examine this element 
 more closely. In 1823 the literature on uranium was greatly 
 enriched by the labors of Berzelius 6 7 and Arfvedson,* 
 the latter estimating its equivalent which he found equal 
 to 2711 (0 = 100). The non-metallic* nature of this metal 
 (if the expression may be allowed), its high atomic weight 
 and other discrepancies gave rise to doubts, but it was 
 not until 1840 when Peligot 8 made known his remark- 
 able discovery that the doubts were confirmed and the 
 discrepancies explained. Peligot found that the sub- 
 stance till then considered as metallic uranium was in 
 reality an oxide of the true metal and he showed how 
 the latter might be obtained. 
 
 Since this date uranium has been a more frequent sub- 
 
 1 Beitrage zur chemischen Kenntniss der Mineral-Korper, Vol. II, 
 p. 197. 
 
 2 Neue Gegenstande der Chemie, Yol. I, p. 1. Yol. IX, p. 36. 
 
 3 Gehlen, neues allgemeines Journ. d. Chem., Vol. IY, pp. 17 et 134. 
 
 4 Schweigger’s Journ. f. Chem. u. Phys., Vol. XLIV, p. 35. 
 
 5 Schweigger’s Journ. f. Chem. u. Phys, Vol. XLIY, p. 1. 
 
 6 Poggend. Annal., Yol. I, p. 359. 
 
 7 Poggend. Annal., Yol. I, p. 245. 
 
 8 Annal. de chim. et de phys., Ill, Yol. V, p. 5. 
 
8 
 
 ject of research. R am m els berg , 1 Ebelmen , 2 Wert- 
 heim , 3 Kuhn , 4 Patera , 5 Drenkmann 6 and others 
 have published their investigations, more or less extensive, 
 on this subject. 
 
 It is not my object in this dissertation to give a more 
 complete history of the element uranium, much less to 
 enumerate its various salts, but I will briefly notice its 
 most important compounds with the halogens which stand 
 in close analogy to the fluorine compounds herein dis- 
 cussed. Before entering upon a description of these salts, 
 it will not be out of place to detail the method employed 
 for procuring the nitrate of uranium which forms the 
 starting point in their preparation. 
 
 1 Poggend. Anna]., Yols LV, LYI et LIX. 
 
 * Annal. d. Chem. u. Pharm , Yol. XLIII, p. 286. 
 
 3 Journ. f. prakt. Chemie,' Vol. XXIX, p. 209. 
 
 4 Anna], d. Chem. u. Pharm., Vol. XLI, p. 337. 
 
 5 Journ. f. prakt. Chemie, Vol. LXI, p. 397 ; Chem. Centralbl. 1856 etc. 
 
 6 Zeitschr. f. d. gesammten Naturw., Vol. XVII, p. 113. Jahresber. 
 1861, p. 255. 
 
EXTRACTION OF URANIUM FROM 
 PITCHBLENDE. 
 
 The only mineral which occurs in sufficient abundance 
 to be employed as a source of uranium is the well known 
 pitchblende (uranpecherz). I received through the kindness 
 of Prof. Wohler a quantity of pitchblende from Joachims- 
 thal in Bohemia. It was of a brownish black color with 
 a dull metallic 'lustre and remarkably free from gangue. 
 The finely pulverized mineral was digested in a porcelain 
 vessel with concentrated sulphuric and nitric acids until 
 the greater portion was dissolved; the excess of sulphuric 
 acid was then expelled by heat. 
 
 The mass was treated with water and the filtrate from 
 the white residue was heated and saturated with sulphu- 
 retted hydrogen. After standing twenty four hours it was 
 filtered, the iron and uranium in solution were oxidized 
 with chlorate of potassium and hydrochloric acid while 
 boiling, and then thrown down by an excess of ammonia. 
 This mixed precipitate was well washed and digested with 
 a strong hot solution of carbonate of ammonium until the 
 precipitate assumed the appearance of oxide of iron. The 
 hot solution of uranium was then quickly filtered and yellow 
 crystals of the double salt carbonate of uranium and ammo- 
 nium (U0) 2 G0 3 + 2 (NH 4 ) 2 €0 3 deposited on cooling. 
 The mother liquid united to the wash -water (which was 
 collected separately) yielded by boiling a precipitate of 
 
10 
 
 hydrated oxide of uranium, U 2 0 3 H 2 Q. By calcining 
 these two salts and dissolving the green oxide formed in 
 nitric acid , large crystals of nitrate of uranium (U0) N0 3 
 were obtained which were puritied by recrystallization. * 
 
 Advantage was taken of the comparatively large scale 
 of operations to submit the several residues to a careful 
 qualitative analysis and with the following results. The 
 first white insoluble portion was found to consist chiefly 
 of sulphate of lead, with small quantities of bismuth and 
 lime. The precipitate by sulphuretted hydrogen contained 
 arsenic, copper, bismuth, a trace of selenium and a not in- 
 considerable quantity of silver. Whether the latter formed 
 a constituent of the pitchblende, or whether its presence 
 should be attributed to the fact that the mineral came 
 from the neighborhood of silver mines , I could not deter- 
 mine. The filtrate from the mixed principitate of iron 
 and uranium contained manganese and magnesia. On trea- 
 ting the green oxide with nitric acid, it was not comple- 
 tely dissolved. The yellowish residue was melted with 
 carbonate of sodium, dissolved in hot water, and after 
 filtering from the uranate of sodium which formed, the 
 solution gave with chloride of ammonium the reaction 
 characteristic of vanadium. 
 
 To recapitulate: the pitchblende from Joachimsthal con- 
 tained arsenic, selenium, lead, copper, bismuth, silver, 
 uranium, iron, manganese, a trace of vanadium, magnesia- 
 lime and silicic acid. 
 
 Wohler’s ^Mineral Analyse in Beispielen* p. 156 et seq. 
 
11 
 
 I. URANIUM AND CHLORINE. 
 
 Bichloride of uranium, UC1 2 , (protochloride of ura- 
 nium, UC1) discovered byPeligot forms the material for 
 the preparation of the metal. It is prepared by heating 
 a mixture of the protoxide or of the green oxide with char- 
 coal in a tube through which a current of dry chlorine is 
 passing. It is a dark green volatile body crystallizing in 
 octahedra and exceedingly deliquescent in a moist atmo- 
 sphere. Its solution is decomposed by evaporation with 
 disengagement of hydrochloric acid. When heated with 
 sodium or potassium it yields metallic uranium in small 
 globules ; but notwithstanding the violence of the reaction 
 the heat developed is not sufficient to fuse the metal, and 
 it can be obtained only in very small quantities. 
 
 A subchloride has been obtained by heating the bichlo- 
 ride in a current of hydrogen, which according to Ram- 
 melsberg has the formula U 2 C1, UC1 but according to 
 Peligot U 2 C1, 2UC1. It dissolves in water with a purple 
 color, but quickly decomposes with disengagement of hy- 
 drogen and precipitation of a reddish powder, the hydrate 
 of the protoxide; the solution at the same time turning 
 green. 
 
 Oxichloride of uranium, (UU) Cl, (old notation 2U 2 0 3 , 
 U 2 C1 3 ) may be obtained by heating the protoxide, U0, 
 in a current of dry chlorine; as thus prepared it is a 
 crystalline, fusible, slightly volatile body, soluble in water, 
 alcohol and ether. Crystals of the same may be procured 
 by evaporating the yellow solution obtained by dissolving 
 the sesquioxide of uranium U 2 0 3 in hydrochloric acid. 
 When heated with potassium this salt yields chloride of 
 
12 
 
 potassium and protoxide of uranium. This compound 
 forms a series of double salts with the chlorides of the 
 alkaline metals, as follows: 
 
 OxiCHLORIDE OF URANIUM AND CHLORIDE OF POTASSIUM, 
 
 (UO) Cl + K Cl + H 2 0 (old notation, U 2 0 2 Cl, K Cl + 2 aq.) 
 
 This salt is prepared by dissolving uranate of potassium 
 in hydrochloric acid and crystallizing the solution over 
 sulphuric acid. The beautiful large greenish yellow rhom- 
 bic plates form best in an acid solution and do not admit 
 of recrystallization. When heated in a closed tube, it 
 melts, parts with its water of crystallization and under- 
 goes partial decomposition. If heated in a current of hy- 
 drogen it is decomposed with evolution of hydrochloric 
 acid and leaves a greenish opaque residue. 
 
 OxiCHLORIDE OF URANIUM AND CHLORIDE OF SODIUM, 
 as well as the corresponding salt of ammonium, have been 
 prepared, but crystallize with great difficulty being deli- 
 quescent. 
 
 II. URANIUM AND BROMINE. 
 
 Bibromide of uranium, UBr 2 (Protobromide of uranium 
 UBr) was first prepared by Hermann.* It is obtained 
 by heating protoxide of uranium in a current of dry bro- 
 mine gas, and constitutes a brownish crystalline mass 
 which emits fumes in the air and deliquesces. 
 
 Hydrated bibromide of uranium, UBr 2 -[-4H 2 0 (Hy- 
 drated protobromide of uranium, UBr+4HO). Rammels- 
 berg obtained this salt by dissolving the hydrate of the 
 
 * Inaug. Dissertat. Gottingen 1861. 
 
13 
 
 protoxide in hydrobromic acid and evaporating the green 
 solution in a desiccator. 
 
 Oxibromide of uranium, (UO)Br (old notation, 2U 2 0 3 
 U 2 Br 3 ) has been prepared by dissolving the hydrated 
 sesquioxide in hydrobromic acid. It crystallizes in yellow 
 deliquescent needles. Whether crystallized double salts 
 can be obtained with the bromides of the alkaline metals 
 has not been examined. 
 
 III. URANIUM AND IODINE. 
 
 The jonly compound of uranium and iodine as yet pre- 
 pared is a bi-iodide UI 2 (protoiodide UI,) containing water 
 and obtained by Rammelsberg in treating the hydrated 
 protoxide with hydriodic acid. Its (properties have not 
 been completely described. 
 
 IV. URANIUM AND CYANOGEN. 
 
 No compound of uranium and cyanogen has been yet 
 procured. 
 
 Y. URANIUM AND FLUORINE. 
 
 (HISTORICAL.) 
 
 The fluorine compounds of uranium have been very little 
 studied. The first notice of a compound of uranium and 
 fluorine is made by Berzelius in his “Researches on 
 Hydrofluoric Acid and its most remarkable Compounds’ 
 which appeared in the first volume of Poggendorf’s An- 
 nalen in 1824. * He briefly describes the oxifluoride of 
 
 * The original reads: “Untersuchungen dber die Flussspathsaure und 
 deren merkwiirdigsten Verbindungen”. 
 
14 
 
 uranium as soluble in water and forming a yellow uncryst- 
 allizable solution. Later (1845) in his “Lehrbuch der 
 Chemie” he repeats the facts before stated, gives the for- 
 mula U 2 F1 3 + 2U 2 0 3 and adds that the solution yields 
 with the fluorides of the alkaline metals yellow crystal- 
 lizable double salts. Berzelius also describes the silico- 
 fluoride of uranium as a bluish green precipitate and men- 
 tions further that the “protofluoride” (bifluoride) is unknown. 
 
 No chemist appears to have more closely examined these 
 compounds until 1861 when Hans Hermann published his 
 dissertation “On some Compounds of Uranium”, in which 
 he examined the action of hydrofluoric acid on the proto- 
 sesquioxide of uranium and describes the “protofluoride” 
 (bifluoride) as a “sesquifluoride” having the formula U 2 Fl 3 . 
 
 He gives the method of preparation and of analysis (though 
 unfortunately no figures) and adds that this “sesquifluoride” 
 contains water which is only expelled by a temperature ot 
 200° C. I trust however it will be satisfactorily demon- 
 strated in the following pages that the substance in ques- 
 tion is an anhydrous bifluoride. 
 
15 
 
 BIFLUORIDE OF URANIUM. £Fl 2 
 
 (PROTOFLUORIDE OF URANIUM. UF1.) 
 
 Preparation I. Hydrofluoric acid in solution acts upon 
 the green oxide of uranium with considerable vigor, caus- 
 ing an appreciable elevation of temperature; a yellow so- 
 lution is formed together with an insoluble green powder 
 which latter is the object of our immediate attention. If 
 the acid employed be somewhat concentrated, the yellow 
 solution is sirupy and admits of filtration, but it is nearly 
 impossible to wash the precipitate upon the filter for it 
 possesses the property of passing through the pores of the 
 paper even if double or fourfold filters are employed. 
 Long continued boiling of the solution with the precipitate 
 does not prevent its persistently running through the filter. 
 By operating upon comparatively large quantities, suffi- 
 cient of the bifluoride was collected for examination and 
 analysis; but it was far from being pure, and hence the 
 figures given in the analyses of the salt as thus prepared 
 are inaccurate. 
 
 Properties. The bluish green powder is insoluble in 
 water and scarcely attacked by dilute acids ; even concen- 
 trated nitric acid dissolves it but slowly. When boiled with 
 a solution of caustic soda, it is decomposed and insoluble 
 black protoxide of uranium is formed which is dehydrated 
 by continued heating. The solution contains fluoride of 
 sodium. If heated strongly on platinum foil it is decom- 
 posed with loss of fluorine and formation of the green 
 oxide, without melting. When heated in a closed tube 
 
16 
 
 it is found to contain no water.- The green powder being 
 in an exceedingly fine state of division is hygroscopic. 
 
 Analysis. The salt having been dried at 100 0 C. a 
 weighed quantity was dissolved by the aid of heat in con- 
 centrated nitric acid. The solution was diluted, the ura- 
 nium precipitated with a slight excess of ammonia and 
 this precipitate was washed partly by decantation partly 
 on the filter with a dilute solution of chloride of ammo- 
 nium. The uranate of ammonium was dried and ignited 
 (with the filter) in a platinum crucible and weighed as 
 
 uou 2 o 3 . 
 
 I. 0.8553grm. substance gaveO.7368 grm. U 3 0 4 =73.1$) U 
 
 II. 1.1845 „ 
 
 >5 » 
 
 1.0310 „ „ =73.8 „ tf 
 
 III. 0.8270 „ 
 
 n r> 
 
 0.7197 „ „ =73.8 „ e 
 
 0.8270 „ 
 
 r> r> 
 
 0.3820 „ Ga FI 2 =22.5 „F1 
 
 The formula 
 
 e 2 Fi 6 
 
 requires 67.7 % U 
 
 
 (U0>F1 2 
 
 » 68.9 „ „ 
 
 » „ tJFl 2 -f-H 2 0 „ 68.1 „ „ 
 
 but „ „ UF1 2 „ 75.9 „ „ and 
 
 24.1 „ FI. 
 
 Therefore although the figures are far from satisfactory a 
 glance shows the formula UF1 2 to be without doubt the 
 true one. 
 
 Preparation II. Bifluoride of uranium may be obtained 
 in a state of purity by reducing the oxifluoride of uranium 
 by means of bichloride of tin. For this purpose the yellow 
 solution resulting from the action of hydrofluoric acid on 
 the green oxide of uranium, is heated in a platinum vessel 
 with bichloride of tin as long as the green bifiuoride falls. 
 If hydrofluoric acid is added from time to time during the 
 reduction, the whole of the uranium is precipitated and 
 the filtrate is colorless, containing only the per-salt of tin. 
 
17 
 
 Instead of the solution of the oxifluoride obtained as 
 above mentioned, a solution of uranate of ammonium (or 
 even of the double salt of carbonate of uranium and ammo- 
 nium) in hydrofluoric acid may be employed with equal 
 advantage. The following equation shows the reaction 
 which most probably takes place: 
 
 2(U0)F1 + 2HF1 -f 2HC1 + SnCl 2 = 2(UF1 2 ) + SnCl 4 +2H 2 O 
 
 As thus prepared the precipitate may be washed upon 
 a filter without the least difficulty, and its behavior with 
 reagents proves its identity with the salt obtained by the 
 preceding method. 
 
 Analysis. The uranium was estimated in this salt pre- 
 cisely as in the previous analysis. The fluorine was deter- 
 mined in a separate portion as follows: a weighed quan- 
 tity of the salt dried at 100 0 C. was boiled with a strong 
 solution of caustic potassa until the green color entirely 
 disappeared, and the black* protoxide of uranium was col- 
 lected on a filter and washed with boiling water. This 
 precipitate was weighed but found to contain potassa. 
 
 The filtrate was nearly neutralized with acetic acid and 
 the fluorine thrown down by chloride of calcium. Car- 
 bonate of potassium in excess being present (the potassa 
 having absorbed carbonic acid from the air, its addition 
 is superfluous) carbonate of calcium falls with the fluoride 
 of calcium, which is absolutely necessary to prevent the 
 latter passing through the filter. The mixed precipitate 
 was dried and ignited with the filter. The carbonate of 
 calcium was dissolved out with acetic acid, the excess of 
 acid driven off by evaporating nearly to dryness on a water- 
 bath, and the fluoride of calcium was then brought upon 
 a filter and washed until the filtrate no longer gave a 
 
 2 
 
18 
 
 precipitate with oxalic acid. The precipitate was again 
 ignited and weighed. The following are the results ob- 
 tained. 
 
 I. 0.7920 giro, substance gave 0.3910 GaFl 2 = 24.0 % FI 
 
 II. 0.7778 grm. „ „ 0.6936 H 3 0 4 = 75.5 „ V 
 
 III. 0.7200 grm. „ „ 0.6484 U 3 0 4 = 76.4 „ U 
 
 The formula UF1 2 requires the following percentage: 
 
 Calculated. 
 
 I. 
 
 Found. 
 
 II. 
 
 III. 
 
 U = 120. 75.9 
 
 .... 
 
 75.5 
 
 76.4 
 
 Fl 2 = 38. 24.1 
 
 24.0 
 
 .... 
 
 .... 
 
 158. 100.0 
 
 
 
 
 Preparation III. Hydrofluoric 
 
 acid 
 
 acts upon the prot- 
 
 oxide of uranium very slowly and yields bifluoride of ura- 
 nium.* As thus prepared it has the property of passing 
 through filtering paper. No analysis of it was made. 
 
 Preparation IV. Hydrofluoric acid converts freshly pre- 
 cipitated hydrated protoxide of uranium into the bifluoride 
 immediately. The green precipitate formed also possesses 
 the property of passing through filters. I did not consider 
 an analysis of this necessary. 
 
 Preparation V. Hydrofluoric acid produces in a solu- 
 tion of the bichloride of uranium UC1 2 a green gelatinous 
 precipitate which is so voluminous that a moderately con- 
 centrated solution of the uranium salt solidifies. On adding 
 water and agitating the precipitate it settles; and when 
 washed by decantation or upon the filter retains its gela- 
 tinous form. By drying this precipitate however over sul- 
 
 * Hans Hermann, in his dissertation already referred to, mentions 
 this reaction but maintains the formation of a “ sesquifluoride” which 
 is impossible. 
 
19 
 
 phuric acid in vacuo or at 100° C. it diminishes greatly 
 in volume and yields a greenish powder a shade lighter 
 than when prepared by any of the previous methods. Two 
 estimations of the uranium made in the manner already 
 described gave the following results. 
 
 1.0308 grm. of the salt dried at 100° C. gave 0.8725 grm. 
 of the proto-sesquioxide, which is equal to 71.8 per cent U; 
 and 0.4460 grm. of the same gave 0.3795 grm. of the 
 green oxide or 72.1 per cent U. 
 
 The formula UF1 2 requires 75.9 per cent uranium but 
 the formula 2(UF1 2 ) + H 2 0 requires 71.8 per cent ura- 
 nium, and it would appear that this is a hydrate which 
 only imperfectly loses its water at 100 0 C. 
 
 The water estimations made gave however no satisfac- 
 tory results, and the further examination of this salt was 
 abandoned. 
 
 A subfluoride (?) was obtained by heating the biflu- 
 oride in a current of dry hydrogen. Hydrofluoric acid 
 was given off and a reddish brown powder formed on 
 the surface; by pulverizing the aggregated mass, heating 
 again in hydrogen and repeating the operation several 
 times, the greater portion assumed a reddish color. 
 
 This substance is quite iusoluble in water and scarcely 
 attacked by acids, concentrated nitric acid excepted. It 
 was not further examined but probably corresponds in com- 
 position to the subchloride obtained under similar conditions.. 
 
 2 
 
20 
 
 OXIFLUORIDE OF URANIUM. 
 
 (HO) FI. 
 
 (Old notation, U 2 Fl 3 + 2U 2 0 3 ). Hydrofluoric acid only 
 partially dissolves the green oxide of uranium; the green 
 bifluoride remaining insoluble may be collected on a Alter 
 though as before mentioned the latter cannot be washed 
 out. The yellow solution shows the same reactions as that 
 which Berzelius* obtained by dissolving hydrated sesqui- 
 oxide of uranium in hydrofluoric acid and is evidently 
 identical with it. Accepting the composition of this body 
 given by Berzelius, viz, (U0)F1 its formation is expressed 
 in the following equation: 
 
 U0H 2 0 3 +4HF1 = UF1 2 + 2[(H0)F1] + 2H 2 0 . 
 
 No analysis of this salt was made but a few of its pro- 
 perties were examined. The yellow solution is un- 
 crystallizable , and on evaporation yields a nearly white 
 mass which dissolves again in water without decompos- 
 ing. It is also soluble in alcohol, and on evaporating 
 this solution it furnishes a yellow, transparent, amorph- 
 ous mass which is very deliquescent. This salt re- 
 tains water when dried at 100° C. If heated in a closed 
 tube it is only partially decomposed, the residue being 
 somewhat soluble in hydrochloric acid. When heated on 
 platinum foil, it loses fluorine and the green oxide of ura- 
 nium remains. Finally, when the solution of the salt is 
 heated with tin and hydrochloric acid, the green bifluoride 
 of uranium is precipitated as already mentioned. 
 
 * Poggend. Ann. Yol. I, p. 34. 
 
21 
 
 OXIFLUORIDE OF URANIUM 
 
 AND 
 
 FLUORIDE OF POTASSIUM. 
 
 2(U0)F1 + 3KF1. 
 
 Preparation I. Fluoride of potassium added to a so- 
 lution of the nitrate of uranium produces a heavy crystal- 
 line precipitate of a lemon yellow color. This precipitate 
 being but sparingly soluble, may be washed upon a filter 
 with cold water to free it from an excess of fluoride of 
 potassium and from the nitrate of potassium which forms ; 
 and being more abundantly soluble in hot water it may 
 be purified by dissolving in hot water and allowing the 
 solution to crystallize, either from the hot concentrated 
 solution or by evaporation of the cold solution over sul- 
 phuric acid. 
 
 In preparing this salt it is of advantage to use a slight 
 excess of fluoride of potassium, * the salt being soluble in 
 nitrate of uranium. According to the analysis made, the 
 details of which are given below, this salt was found to 
 
 * The fluoride of potassium employed must be free from silico-fluo- 
 ride of potassium, hence the following precautions observed in its pre- 
 paration. 
 
 Selected crystals of pure fluor spath (as free from quartz as possible) 
 were finely pulverized in an iron mortar and gently heated with con- 
 centrated sulphuric acid in a platinum retort. The hydrofluoric acid 
 was absorbed by distilled water contained in a platinum capsule and 
 after the destination ceased, the acid solution was neutralized with 
 pure carbonate of potassium. If notwithstanding these precautions a 
 small quantity of silico-fluoride of potassium forms, it may be separ- 
 ated by filtering through platinum or gutta-percha funnels. 
 
22 
 
 contain 2(U0)F1 + 3 KF1; its formation maybe therefore 
 expressed in the following equation: 
 
 5 (K FI) + 2 (£0) NO 3 - [2 (UO) FI + 3 K FI ] + 2 K NO 3 
 Preparation II. The oxifiuoride of uranium and po- 
 tassium may also be procured by dissolving freshly pre- 
 cipitated uranate of potassium in hydrofluoric acid, adding 
 fluoride of potassium and crystallizing. The necessity of 
 adding fluoride of potassium is made evident by the fol- 
 lowing equation showing the formation of the salt: 
 K 2 02(0 2 0 3 )+6HF1 + 4KF1-2[2(U0)FM-3KF1]T-3H 2 0 
 Preparation III. The same salt may be procured by 
 adding fluoride of potassium to a solution of the hydrated 
 oxide of uranium in hydrofluoric acid, or to the oxiflu- 
 oride of uranium as obtained by the action of hydrofluoric 
 acid on 4he green oxide of uranium. These methods how- 
 ever possess no advantages over the foregoing. 
 
 In the hope of preparing the salt in question in the dry 
 way, I made the following experiment. A small quantity 
 of the double salt sulphate of uranium and potassium was 
 prepared by heating the nitrate of uranium with concen- 
 trated sulphuric acid and neutralizing with potassa. This 
 double salt was finely pulverized, intimately mixed with 
 fluoride of sodium and some previously dried sulphate of 
 sodium (as a flux), the mixture introduced into a Hessian 
 crucible which was maintained at a red heat for more 
 than an hour and then allowed to cool in the furnace. 
 The result however was unsatisfactory; the greater part 
 of the sulphate of uranium and potassium remained un- 
 changed, with the exception of the formation of a small 
 amount of uranate of sodium near the surface of the mel- 
 ted mass. 
 
23 
 
 Properties. The oxifluoride of uranium and potassium 
 crystallizes in small yellow plates. 1 obtained crystals grouped 
 in three different ways: first , by the cooling of a hot concen- 
 trated solution, a crust of minute crystals formed upon which 
 rested larger individual prisms ; secondly , by the spontaneous 
 evaporation of a cold solution well defined twin crystals formed, 
 easily distinguishable without a magnifying glass though not 
 more than two millemeters in diameter; thirdly, 1 acciden- 
 tally obtained a number of warty concretions consisting of 
 concentric rings of small crystals and completely spherical. 
 They formed at a low temperature. The crystals thus ob- 
 tained are small but often well formed and possess a high 
 lustre but not the brilliant fluorescence peculiar to the cor- 
 responding oxichloride. Containing no chemically com- 
 bined water they do not effloresce. 
 
 I am indebted to Prof. Victor von Lang, who had 
 the kindness to measure crystals of this salt, for the fol- 
 lowing data. 
 
 Crystalline system: Monoclinic. 
 
 a: b:c= 1.375: 1:3.477 
 ac = 99° 40' 
 
 Observed forms = 
 
 (001), (110), (101). 
 
 Fig. 1. 
 
 Calculated 
 
 Observed ^ ; 
 
 
 
 001-101 = 77°0’ 
 
 00M10 = 82° 14' 
 110-110 = 72° 50’ 
 
 77°0' /</■ 
 
 OQO -I A t / X 
 
 ooi i \ 
 
 02 14 
 
 72° 50' \ 
 
 110 
 
 110-101 = 56° 47’ 
 
 o 
 
 GO 
 
 iO 
 
 
 The crystals as seen in fig. 1 are plates, the planes (001) 
 
 predominating. 
 
 The twin crystals of the same salt furnished the following. 
 Crystalline system: Tetragonal. 
 
 a : c = 1:2.0815 
 
24 
 
 Observed forms: (101), (104), (001). 
 
 Fig. 2. 
 
 Calculated Observed 
 
 101-001 =64° 20' 64° 20’ 
 
 101-101 = 51°20’ 51° 20' 
 
 104-001 = 27° 29’ 
 
 101-104 = 36° 51' 36° 50’ 
 
 101- 011 = 79° 11' 78° 30’ 
 
 102- 001 = 46° 8’ 
 
 The crystals are penetration twins formed on a plane 
 
 (102), both individuals equally developped. The planes 
 (104), (001) occur rarely. Optical character negative. 
 
 When heated in a closed tube, the salt melts , forming 
 a red liquid which solidifies and resumes its yellow color 
 on cooling; it undergoes partial decomposition. If heated 
 on platinum foil with free access of air it melts as before 
 and loses its fluorine, an infusible mass remaining which 
 has a deep crimson color while hot and turns orange- 
 yellow on cooling. This yellow residue on examination 
 proved to be uranate of potassium. 
 
 The salt does not decompose in boiling water; it is of 
 neutral composition , but shares the property of other neu- 
 tral uranium salts of reddening slightly blue litmus. The 
 salt in solution does not attack glass even when concen- 
 trated and boiling; hence glass vessels may be employed 
 in examining the salt though platinum ones are necessary 
 in its preparation. The salt is insoluble in alcohol and 
 ether, the former precipitating it finely divided from the 
 aqueous solution. An estimation of the solubility of the 
 salt was made by evaporating a weighed amount of a con- 
 centrated solution and after drying the residue at 100° C 
 weighing the crucible and contents a second time. 
 
25 
 
 Thus, 8.6812 grras of the concentrated solution at 21° C 
 yielded on evaporation 0.9653 grm. of the salt. By calcul- 
 ation, therefore, 100 parts of water at 21° C dissolve 
 12.5 parts of the salt. 
 
 The salt is decomposed by melting with carbonate of 
 sodium, forming uranate and fluoride of sodium. The 
 action of reagents on the solution of the salt is as follows: 
 ammonia produces the usual precipitate of uranate of am- 
 monium; the carbonates of sodium and ammonium do not 
 decompose the salt on boiling: chloride of barium gives 
 even in dilute solutions a voluminous white precipitate which 
 settles in the form of a crystalline powder; this change 
 is accelerated by heating; acetate of lead gives an orange 
 yellow precipitate very soluble in dilute acids, the filtrate 
 still contains uranium; chloride of calcium gives a white 
 transparent precipitate from which it is impossible to filter; 
 solutions of silver , copper , iron , mercury , platinum and 
 zinc are without action; oxalic or formic acids and the 
 direct rays of the sun produce a green precipitate.* 
 
 By heating the salt in a current of hydrogen gas , hydro- 
 fluoric acid is disengaged and the greenish residue con- 
 sists of a mixture of bifluoride of uranium, protoxide of 
 uranium and fluoride of potassium. This experiment de- 
 monstrates most clearly the presence of oxygen. 
 
 Quantitative Analysis, (a) The crystallized salt hav- 
 ing been dried over sulphuric acid, a weighed portion 
 was heated in a platinum crucible with concentrated sul- 
 phuric acid and when the fluorine was completely expelled 
 the excess of acid evaporated. The temperature was gra- 
 
 * See page 33, 
 
26 
 
 dually raised until the crucible was at a low red heat, its 
 contents melting without projections. After dissolving out 
 the contents of the crucible, ammonia was added to throw 
 down the uranium and this precipitate treated as usual. 
 Since uranate of ammonium precipitated in presence of 
 the fixed alkalies has a tendency to combine with them, 
 the green oxide of uranium after having been weighed 
 was dissolved in nitric acid and reprecipitated by ammo- 
 nia, washed, ignited and weighed as before. The second 
 weighing showed a loss of twelve tenths of a milligramme 
 (0.0012 grm.) which is too inconsiderable to affect the ana- 
 lysis and is to be attributed to inaccuracy of manipulation 
 rather than to the presence of potassa in the first precipitate. 
 
 (b) The filtrate was evaporated to dryness in a pla- 
 tinum dish on a water-bath, the residue gently calcined 
 until all chloride and sulphate of ammonium were expelled 
 and the remaining sulphate of potassium was dissolved in 
 a few drops of water filtered into a platinum crucible, 
 again evaporated, ignited and weighed. Since it is ne- 
 cessary to wash the uranate of ammonium with a dilute 
 solution of chloride of ammonium, the estimation of the 
 potassium as just detailed is exceedingly tedious. 
 
 (c) The determination of the fluorine presented many 
 difficulties. The precipitate of fluoride of. calcium obtained 
 by adding chloride of calcium to the solution of the po- 
 tassium salt is in an extremely fine state of division and 
 runs through the filter notwithstanding every precaution. 
 The estimation of the fluorine as fluoride of lead was not 
 deemed sufficiently accurate or available in this case, and 
 the following method was pursued which though imperfect 
 gave such results as warranted its use. A weighed quantity 
 
27 
 
 of the salt was melted with three to four times its weight 
 of carbonate of sodium in a platinum crucible; the melted 
 mass after being cooled was treated with water which 
 dissolved out the fluoride of sodium arid the excess of car- 
 bonate of sodium leaving crystallized uranate of sodium 
 for the most part undissolved. Jhe fluorine was then 
 thrown down in the filtered solution by chloride of cal- 
 cium and the mixed precipitate of carbonate and fluoride 
 of calcium treated exactly as described in the analysis 
 of bifluoride of uranium. 
 
 In the two estimations made the fluoride of calcium 
 was colored yellow oweing to the partial solubility of ura- 
 nate of sodium in carbonate of sodium. 
 
 The results obtained are as follows: 
 
 I. 0.9453 grm. substance gave 0.5542 grm.U 3 0 4 =49.8 
 
 
 n 
 
 „ 0.5040 
 
 ft K 2 S0 4 = 
 
 23.9 B K 
 
 II. 0.6316 „ 
 
 n 
 
 a 0.2450 
 
 F a FI 2 — 
 
 18.9 a FI 
 
 III. 0.6810 „ 
 
 V 
 
 a 0.2680 
 
 a FaFl 2 = 
 
 19.12a FI 
 
 These numbers correspond to the formula 2(U0)F1+3KF 
 as follows: 
 
 Calculated. Found. 
 
 
 
 I. 
 
 II. 
 
 III. 
 
 » 3 = 240. 
 
 49.59 
 
 49.86 
 
 .... 
 
 .... 
 
 0 3 = 32. 
 
 6.62 
 
 .... 
 
 
 .... 
 
 Fl 5 .= 95. 
 
 19.61 
 
 .... 
 
 18.90 
 
 19.12 
 
 K 3 = 117. 
 484. 
 
 24.18 
 
 100.00 
 
 23.90 
 
 
 — 
 
28 
 
 OXIFLUORIDE OF URANIUM 
 
 AND 
 
 FLUORIDE OF SODIUM. 
 
 2(U0)Fl + NaFl + 4H 2 O. 
 
 I. This salt though more difficult to procure than the 
 foregoing, crystallizes far better if one succeeds in em- 
 ploying the proper proportions of its constituents. 
 
 By evaporating a mixture of nitrate of uranium and 
 fluoride of sodium in a desiccator, 1 obtained monoclinic 
 prisms of considerable size and great beauty, but many 
 trials subsequently made were unsuccessful in reproducing 
 them. The analysis having given the above constitution 
 of the double salt, its formation may be expressed by the 
 equation : 
 
 2(U0N0 3 ) + 3NaFl = [2(UO) Fl + NaFl] + 2(NaN0 3 ) 
 
 A solution of uranate of sodium in hydrofluoric acid 
 when slowly evaporated over sulphuric acid furnishes 
 similar crystals, but neither in this case could I find the 
 conditions requisite for their certain formation. This method 
 should theoretically be more advantageous than the pre- 
 vious one in which nitrate of sodium forms and interferes 
 with the crystallization but it did not prove as successful. 
 The reaction is as follows: 
 
 Na 2 0, 2(U 2 0 3 ) + GHF1 = 2 [2(U0)Fl-f NaFl] + 3H 2 0 
 
 Properties. This salt is by no means so stable as the 
 corresponding potassium salt; it decomposes on attempt- 
 ing to recrystallize it, or if its solution is heated, fluoride 
 of sodium crystallizing out separately. 
 
 Prof. Victor von Lang who also measured these crystals 
 has furnished the following data. 
 
29 
 
 Crystalline system: monoclinic, 
 a : b : c - 1.0272 : 1 : 0.5222. ac = 94° 51' 
 
 Observed forms: (100), (110), (111), (132) 
 
 Calculated Observed 
 
 110- 100 = 45°40' 45° 40' 
 
 111. 100 = 69° 20' 69 ° 20' 
 
 111.111 = 51° 20' 51° 20' 
 
 111- 110 = 56° 11' 55° 
 
 132-100 = 97°41' 98° 
 
 132-110 = 58° 19' 00° 
 
 The crystals are juxtaposition twins on 
 the plane (100) and as seen in fig*. 3 appear 
 as thin plates by the predominance of the 
 same plane. 
 
 When heated in a closed tube, it gives off its water of 
 crystallization, and on raising the temperature melts, the 
 residue consisting of uranate of sodium. In a dry atmos- 
 phere it effloresces. Its properties in general resemble those 
 of the potassium salt, and the analysis was simply a repe- 
 tition of that described at length in the preceding section. 
 
 When the crystallized salt is heated at 100 0 C. it loses 
 two atoms of water = 8.4 per cent. 
 
 I. 1.2230 grms. cryst. salt gave 0.8205 U 3 0 4 = 56.9°/oU 
 1.2230 „ „ „ „ 0.2340 Na a S0 4 = 6.2 °/ 0 Na 
 
 The formula 2(U0)F14~NaFl-[-4H 2 0 requires the fol- 
 lowing percentage: 
 
 
 Calculated. 
 
 Found. 
 
 
 = 240, 
 
 56.6 
 
 56.9 
 
 e 2 
 
 c<f 
 
 CO 
 
 11 
 
 7.54 
 
 • • • •- 
 
 Fla 
 
 = 57, 
 
 13.44 
 
 
 
 Na 
 
 II 
 
 to 
 
 03 
 
 5.42 
 
 6.2 
 
 4H 2 0 
 
 = 72, 
 
 17.0 
 
 
 
 
 424 
 
 100.00 
 
 
30 
 
 II. On endeavoring to recrystallize this salt it partially 
 decomposes, and other smaller crystals form containing 
 two atoms less of water. This salt is not efflorescent. 
 The analysis gave the following results: 
 
 1. 1.0755 grms. cryst. salt gave 0.7765 grm. U 3 0 4 = 61.3°/ 0 © 
 II. 0.8699 „ „ „ „ 0.2730 grm. OaFl 2 = 15. 1°/ 0 F1 
 
 These figures correspond to the formula 2(DO)Fl-f NaFl 
 -}-2H 2 0 as follows: 
 
 Calculated. 
 
 U 2 = 240, 61.85 
 
 0 2 = 32, 8.24 
 
 FI 3 = 57, 14.69 
 
 Na = 23, 5.92 
 
 2H 2 Q = 36, 9.30 
 
 388, 100.00 
 
 Found, 
 
 61.3 
 
 15.1 
 
 OXIFLU 0 RIDE OF URANIUM 
 
 AND 
 
 FLUORIDE OF AMMONIUM. 
 
 2 (DO) Fi + NH 4 FI + xH 2 0 (?) 
 
 By dissolving uranate of ammonium in hydrofluoric acid 
 and evaporating the solution over sulphuric acid, but few 
 distinct crystals were obtained. On account of the diffi- 
 culty of preparing this salt in a pure state no quantitative 
 analysis of it was made, but only a few of its properties 
 examined. 
 
 This yellowish imperfectly crystallized mass is very sol- 
 uble in water, less soluble in a solution of hydrofluoric 
 acid and quite insoluble in alcohol. When heated on plati- 
 num foil it is completely decomposed the green oxide 
 
31 
 
 remaining. When heated in a closed tube, water is at 
 first given off, fluoride of ammonium sublimes and con- 
 denses on the sides of the tube. The residue in this case 
 is also the proto-sesquioxide of uranium. 
 
 This salt has most probably a composition corresponding 
 to the foregoing salts of potassium and sodium, which 
 may be expressed in general terras as follows: x(TO)Fl 
 -f-yRFl-|-zH 2 0. <C R” being the alkali metal. 
 
 OXIFLUORIDE OF URANIUM 
 
 AND 
 
 FLUORIDE OF BARIUM. 
 
 4 (TO) FI + 3 RaFl 2 + 2 H 2 0 
 
 Preparation. The addition of chloride of barium to 
 a solution of the oxifluoride of uranium and potassium 
 produces a voluminous lemon yellow precipitate which 
 gradually settles in the form of a crystalline powder. This 
 precipitate being quite insoluble in cold water may be 
 washed on the filter until free from chloride of barium 
 and when dried at 100° C. forms a yellowish white powder 
 which under a powerful microscope resolves into minute 
 crystals, if, in preparing this salt, the oxifluoride of ura- 
 nium and potassium is not perfectly free from fluoride of 
 potassium, the insoluble uranium salt will be mixed with 
 fluoride of barium which being equally insoluble cannot be 
 separated. 
 
 Properties. Hot water dissolves only a trace of this 
 salt, but it is quite soluble in dilute acids. This acid 
 solution yields a white precipitate of sulphate of barium 
 with sulphuric acid, and the filtrate a yellow precipitate 
 
32 
 
 of uranate of ammonium with ammonia. On heating the 
 salt in a closed tube, water is disengaged, and at a higher 
 temperature hydrofluoric acid. The salt does not melt 
 during the decomposition. 
 
 Analysis. The quantitative analysis was conducted as 
 follows; a given quantity was dissolved in dilute hydro- 
 chloric acid, and the solution being heated to boiling, the 
 barium was thrown down with a slight excess of sul- 
 phuric acid. The uranium was precipitated by ammo- 
 nia and estimated as U 3 0 4 . The fluorine was estimated 
 in the filtrate in the same manner as in the analysis of 
 the preceding salts. The salt dried at 100° C. still retains 
 water which was estimated according to a method proposed 
 and employed by Berzelius and recommended byH. Rose.* 
 A weighed quantity of the salt was introduced into a 
 porcelain crucible and well mixed with four to five times 
 its weight of previously calcined litharge. The crucible 
 was weighed first empty then with the salt and then after 
 the addition of the oxide of lead; the covered crucible 
 was cautiously brought to a low red heat and after cool- 
 ing in the desiccator was weighed again. The difference 
 in weight before and after calcining is due to the water 
 driven off, the fluorine being retained by the lead. 
 
 Result of the analyses: 
 
 I. 0.7222 grin, substance gave 0.4178 BaS0 4 =33.9°/oBa 
 
 „ 0.3564U 3 O 4 =41.8 „U 
 „ 0.3720 BaS0 4 = 35.3 „ Ba 
 
 „ 0.3140U 3 0 4 =41.1 „ U 
 
 „ 0.2110CaFl 2 =15.9 „ FI 
 
 „ O.O192H 2 0 = 3.4 „ H 2 0 
 
 n r> ' r> 
 
 II. 0.6427 „ „ 
 
 5? r> 
 
 ?) » » 
 
 III. 0.5538 „ 
 
 * Chimie Analytique. Vol. II, p. 758. 
 
33 
 
 The formula 4(UO)F14 3BaFl 2 +2H 2 0 corresponds to 
 the figures obtained as follows: 
 
 Calculated. 
 
 
 I. 
 
 Found. 
 
 II. 
 
 III. 
 
 II 
 
 ►Ji- 
 
 ao 
 
 o 
 
 40.6 
 
 41.8 
 
 41.1 
 
 .... 
 
 = 64, 
 
 5.4 
 
 .... 
 
 .... 
 
 . . . • 
 
 Fl 10 = 190, 
 
 16.1 
 
 .... 
 
 15.9 
 
 . , . . 
 
 Sa 3 = 411, 
 
 34.8 
 
 33.9 
 
 35.3 
 
 .... 
 
 2H 2 0 = 36, 
 1181. 
 
 3.1 
 
 100.0 
 
 — 
 
 .... 
 
 3.4 
 
 FLUORIDE OF URANIUM AND POTASSIUM, 
 
 2(UF1 2 ) + KF1. 
 
 Preparation. Formic acid produces no precipitate in 
 the solution of the oxifluoride of uranium and potassium, 
 but if the acidified solution is placed in the direct rays 
 of the sun decomposition begins almost immediately; a 
 green precipitate gradually falls , and if the action is pro- 
 longed, the solution becomes colorless and retains only 
 a trace of uranium. 
 
 The precipitate washed upon a filter and dried at 100° G 
 forms a green impalpable powder much resembling the bi- 
 fiuoride of uranium. This reaction appears to be best 
 effected in dilute solutions. 
 
 Properties. This double fluoride is quite insoluble in 
 water and in dilute acids. It dissolves with difficulty in 
 concentrated boiling hydrochloric acid , but is more easily 
 decomposed with concentrated sulphuric acid which ex- 
 pels the fluorine and yields a green solution. Ammonia 
 produces in this solution a black precipitate of hydrated 
 
 3 
 
34 
 
 protoxide of uranium and the filtrate on evaporation yields 
 sulphate of potassium. 
 
 When heated on platinum foil the salt melts, hydrofluoric 
 acid is disengaged and the yellow residue consists of ura- 
 nate of potassium. This reaction distinguishes this double 
 salt in a marked manner from the bifluoride. When heated 
 in a closed tube, i. e. without access of air, the decom- 
 position is different. The salt melts and gives off hydro- 
 fluoric acid as before, but the residue consists of black 
 protoxide of uranium suspended in fused fluoride of po- 
 tassium. If heated with a solution of caustic soda, it is 
 decomposed with formation of the black protoxide, while 
 the fluorine goes into solution. When heated in a current 
 of dry hydrogen, it melts, hydrofluoric escapes and the 
 same reddish powder is formed which was obtained by 
 treating the bifluoride of uranium in a similar manner. 
 On cooling the mass was found to be green within, the 
 surface only having been attacked. No further examination 
 of this was made. 
 
 Analysis. The analysis of this salt was made in ex- 
 actly the same manner as that of the oxifluoride, only 
 remarking that the solution in sulphuric acid was oxidized 
 with fuming nitric acid before throwing down the uranium 
 with ammonia. The potassium was estimated in the or- 
 dinary way as sulphate. 
 
 The following figures show the results of the analysis. 
 0.7535 grm substance gave 0.5640 grm U 3 0 4 = 63.4 °/ 0 U 
 „ „ „ „ 0.1852 „ K 2 S0 4 = 11.0 „ K 
 
 The formula 2(UF1 2 ) + KF1 requires the following per- 
 centage : 
 

 
 35 
 
 
 
 Calculated. 
 
 
 Found. 
 
 e 2 
 
 = 240. 
 
 64.1 
 
 63.4 
 
 Fl 5 
 
 = 95. 
 
 25.5 
 
 
 K 
 
 = 39. 
 
 10.4 
 
 11.0 
 
 
 374. 
 
 100.0 
 
 
 QUANTITATIVE REDUCTION 
 OF THE 
 
 OXIFLU ORIDE OF URANIUM AND POTASSIUM. 
 
 As already remarked the reducing action of formic acid 
 in the sunlight is very complete so that only a trace of 
 uranium remains in solution, and the resulting salt being 
 quite insoluble I conceived the idea of effecting the reac- 
 tion quantitatively , and as the figures below indicate, suc- 
 ceeded beyond expectation. 
 
 The method of making this quantitative analysis by means 
 of the sunlight needs no lengthy description. A quantity 
 of the potassium double salt was dried at 100° C, weighed, 
 dissolved in water acidified with formic acid and the solution 
 exposed to the direct rays of the sun during two (short 
 winter) days. So long a time was necessary for although 
 decomposition begins at once and is at first rapid it grad- 
 ually decreases in intensity as the solution becomes weak. 
 The green precipitate was collected on a filter previously 
 dried at 100° C and weighed and after being washed with 
 cold water, the filter and contents were dried at 100° C 
 and weighed as before. Thus two weighings sufficed to 
 give data for calculating the formula of the salt and at 
 the same time to confirm the formula adopted for the 
 oxifluoride. 
 
 3 * 
 
36 
 
 1.0635 giro, oxifluoride gave 0.8205 grm. of the precipitate. 
 
 W employed aK is t0 its et l uivalent as preefpHafe is to its 6< * uiTalent 
 
 1.0635 : 484 = 0.8205 : X 
 
 x = 373.6 
 
 The formula 2(UF1 2 ) + KF1 has the equivalent = 374.0 
 A second analysis was made in like manner. 1.1530 grm. 
 of the oxifluoride gave 0.8783 grm. of the precipitate. In 
 place of stating the proportion as above it may also be 
 put thus : 
 
 Equiv. of . , equiv. of double weight of . , weight of 
 
 oxifluoride s 0 fluoride as oxifluoride IS 0 precipitate 
 
 484. : 374. = 1.1530 : a; 
 
 x — 0.8888 grm. 
 
 whereas the weight actually received = 0.8783 grm. 
 
 REDUCTION OF THE OXIFLUORIDE OF URANIUM 
 AND POTASSIUM BY MEANS OF OXALIC ACID 
 AND SUNLIGHT. 
 
 • Oxalic acid with the aid of sunlight decomposes the oxi- 
 fluoride of uranium and potassium in much the same man- 
 ner as formic acid, but with the formation of secondary 
 products. The green insoluble fluoride of uranium and 
 potassium falls as before, but after the decomposition has 
 reached a certain stage, a brownish red precipitate also 
 forms. 
 
 This proved to be hydrated protoxide of uranium, dis- 
 covered by Ebelmen* and obtained by him through the 
 
 * Annal. d, Chein. u. Pharm. Yol. XLIII. 
 
37 
 
 action of the sun’s rays on a solution of the oxalate of 
 uranium. This hydrate however being soluble in dilute 
 acids is easily separated from the quite insoluble fluoride. 
 
 During the decomposition by oxalic acid a considerable 
 quantity of carbonic acid disengages; of course carbonic 
 acid must be also set free when the decomposition is ef- 
 fected with formic acid, but only half as much is theoret- 
 ically formed and this is probably absorbed by the water 
 for in no case did I observe its escape. The following 
 equations giving the action of these two acids are prob- 
 ably not absolutely correct but only approximatively so, 
 since Ebelmen mentions the formation of carbonic oxide 
 as well as of carbonic acid. 
 
 With oxalic acid: 
 
 [ 2 (GO) FI + 3 K FI] + 3(G 2 H 2 0 4 ) = [2 (UF1 2 ) + K FI] 
 
 + 2(KHG 2 0 4 )4-2H 2 0 + 2G0 2 
 With formic acid: 
 
 [ 2 (DO) FI + 3 K FI] + 3 (G H 2 0 2 ) = [ 2 (D Fl 2 ) + K FI] 
 
 4- 2 (KGHG 2 ) 4“ 2 H 2 G 4~ GG 2 
 
 An experiment made with the object of effecting the 
 reduction at a high temperature without the aid of sun- 
 light, was unsuccessful. A solution of the oxifluoride acid- 
 ified with formic acid was heated in a sealed tube at 
 100° C. and afterwards at 120° C. but without producing 
 the least change. 
 
 In a sealed tube which stood for several weeks in dif- 
 fuse daylight a small quantity of the green precipitate 
 formed, the glass being at the same time somewhat at- 
 tacked by the fluorine. On opening the tube carbonic 
 acid gas escaped from the solution. 
 
 The oxichloride of uranium and potassium corresponding 
 
38 
 
 to the fluorine salt and having the formula (U0)C1 + KC1 
 + 2 aq could not be reduced by means of formic or oxalic 
 acids in the sunlight; nor by heating an acidified solution 
 in a sealed tube at 120° C. 
 
 FLUORIDE OF URANIUM AND SODIUM. 
 
 2(UFl 2 ) + NaFl (?) 
 
 When a solution of the oxifluoride of uranium and so- 
 dium is acidified with formic or oxalic acids and exposed 
 to the direct rays of the sun, a reduction takes place in 
 much the same manner as in the case of the potassium 
 salt. The properties too of the precipitate differ little from 
 those of the corresponding potassium compound, but it 
 appears to be somewhat soluble in water since the solu- 
 tion becomes green and not colorless after a lengthened 
 exposure. Neither does it melt when heated on platinum 
 foil but simply loses fluorine and leaves uranate of so- 
 dium characterized by its yellow color. 1 made no ana- 
 lysis of this salt, but it probably possesses the composi- 
 tion given in the above formula. 
 
 As much as the application of Peligot’s uranyle theory 
 simplifies the formulae of many compounds of uranium 
 they become still more simple when combined with the 
 modern double atomic weights and the unitary system of 
 notation. The following table of a few of the most im- 
 portant salts of uranium gives in the first column the 
 old names and formulae and in the second the new. 
 
39 
 
 0 0 ob 0 O 
 
 ^ o 
 0 
 
 0 
 
 w 
 
 + 
 
 6 
 
 0 
 
 0 
 
 O 
 
 w 
 
 0 — , 
 
 0 0 
 0 0 
 
 0 
 
 w 
 
 CO 
 
 + 
 
 pH 
 
 0 
 
 0 
 
 CM 
 
 0 
 
 3 
 
 0 
 
 + 
 
 0 
 
 0 
 
 &, 
 
 CM 
 
 0 
 
 C/fe 
 
 0 
 
 0 
 
 03 
 
 a ^ 
 
 3 X 
 
 *a 3 
 
 3 o 
 
 V V 
 
 P 0 
 
 03 
 
 33 
 
 03 
 
 P3 
 
 3 3 
 
 P 0 
 o’ a ft.q 
 
 c« P-H r-H O 
 S ^ VTj 
 
 CO CO CO PQ 
 
 © 
 
 "0 
 
 J13 
 
 
 
 3 aT* 
 
 l ~“‘' 03 
 
 0, 
 
 3 
 
 3 
 
 s 
 
 3 
 
 a 
 
 
 P 
 
 3 
 
 3 
 
 a 1 
 
 3 
 
 Vh 
 
 a 
 
 *C» 
 
 CO 
 
 3 
 
 h-s 
 
 
 © 'a 
 
 0-H P4— ( 
 
 .3 3 
 
 c n 
 
 n <4-h 
 
 O 
 
 o 
 
 
 O 
 
 O 
 
 c$ o 
 
 <v 
 
 a? 
 
 O 
 
 CL, 
 
 03 
 
 3 
 
 03 
 
 03 
 
 -4-^ 
 
 © 03 
 
 *v 
 
 3 
 
 *G 
 
 33 
 
 *H 
 
 o 
 
 33 33 
 
 *Eh "a 
 
 Ph i-Q 
 
 pa ’v 
 
 o 
 
 o 
 
 3 
 
 3 
 
 o 
 
 O 
 
 3 C 
 
 3 
 
 3 
 
 3 
 
 CP 
 
 3 3 
 
 3 J3 
 
 o 
 
 o 
 
 
 0 
 
 0 pH 
 
 PH 
 
 a . 
 
 o 
 
 oo 
 
 J! O O ^ 
 
 0 0 P D 
 
 m 
 
 6 Q 
 0 0 
 
 .5 ^ 
 
 p pa 
 
 ITS os 
 
 a © 
 
 o 
 
 <M 
 
 0 
 
 CM 
 
 + 
 
 CO 
 
 o 
 
 c* 
 
 0 
 
 or 1 
 
 oS 
 
 CM 
 
 + 
 
 Q 
 
 O 
 
 C* 
 
 0 
 
 + 
 
 O 
 
 M 
 
 O 
 
 0* 
 
 CM 
 
 + . 
 CO 
 
 PH 
 
 0 
 
 O O 
 
 03 03 
 
 H-H -v> 
 
 03 oS 
 0 0 
 3 3< 
 3 13 
 
 GG CG 
 
 0 
 
 W 
 
 o 
 
 0 
 
 
 CO 
 
 CO 
 
 GO 
 
 CO 
 
 o 
 
 + 
 
 4- 
 
 o 
 
 CG 
 
 / N 
 
 0 
 
 0 
 
 3 
 
 CO 
 
 O 
 
 CO 
 
 O 
 
 <N 
 
 C* 
 
 o 
 
 0 
 
 + 
 
 0 
 
 0 
 
 0 
 
 p' 
 
 
 
 CM 
 
 0 
 
 
 
 03 
 33 
 CD 
 
 a ^ 
 
 3 X 
 
 ■S5 . . 
 
 3 O <o i — i 
 03 3 
 
 03 
 
 o 2 « 
 
 3 fe P> 
 
 x a> rQ ~ 
 
 o o a 'd o 
 
 & p, « 3 ■« . 
 2 *« 
 
 P5 
 
 0 
 
 
 
 CM 
 
 3 
 
 
 pa 
 
 
 a 
 
 a 
 
 a 
 
 .2 
 
 3 
 
 * g 
 
 a a 
 3 *a 
 
 iP 
 
 3 
 p ’ 
 
 3 
 
 v 
 
 3 
 
 CO 
 
 CO 
 
 3 
 
 ■+* 
 
 3 S 
 
 b o 
 
 3 
 
 Vi 
 
 P < 
 
 <*-H 
 
 O 
 
 a) 
 
 O 
 
 0 
 
 'P 33 
 
 O rg 
 
 2 0 
 «H-H 
 
 o ^ 
 
 «H-H 
 © , 
 
 0 P-i CG CG O Ph O 
 
 3 « *C £ 
 C 'O o iS 
 
 o -C 3 £ 
 
 0 3 ^ 3 
 
 " -S3 -Js qa 
 
 ° 2 3 
 
 0 o 
 
 M 
 
 o 
 
 -v 
 
 © 
 
 Ph 
 
 o 
 
 <v 
 
 -v 
 
 3 
 
 0 
 
 J0 
 
 "a 
 
 GG 
 
 O 
 
 03 
 
 -V 
 
 3 
 
 0 
 
 3 
 
 'a 
 
 GG 
 
 Nitrate of sesquioxide U 2 0 3 N0 5 Nitrate of uranyle (U-O-)NO; 
 
 etc. etc. 
 
3 0112 072830224 
 
 
 40 
 
 On comparing the chlorine with the fluorine compounds 
 (the bromides and iodides being as yet too little studied) 
 the most marked difference is the greater stability of the 
 latter. While the bichloride of uranium is volatile, very 
 soluble and even deliquescent, the corresponding fluoride 
 is not in the least volatile and is quite insoluble in water. 
 
 The double salts of potassium too show the same dis- 
 tinctive character. The chloride of uranyle and potassium 
 is obtained with greater difficulty and cannot be recrys- 
 tallized, while the fluorine salt forms easily and crystall- 
 izes repeatedly from its solutions. 
 
 It is certainly remarkable that while the fluorine salt 
 exhibits such a sensibility to the sun’s rays (in presence 
 of a reducing agent) the chlorine salt does not possess 
 this in the smallest degree. Might not this double fluorine 
 salt be employed to estimate the power of the sun’s ac- 
 tinic rays? For as we have seen, the green precipitate 
 which forms only in the sunshine is so insoluble as to 
 admit of effecting the reaction quantitatively.