Joseph William Mellor.

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the corresponding higher fluorides are formed. Other suggestions have also been made
to prepare fluorine by chemical processes O. T. Christensen 17 proposed heating the higher
double fluorides of manganese ; A. C. Oudemans, potassium fluochromate ; and H. Moissan,
platinum fluophosphates. About 1883, H. B. Dixon and H. B. Baker made an attempt
to displace fluorine by oxygen from uranium pentafluoride, UF 6 . A. Jiimdriimml trinl (In-
action of boron trifluoride on lead oxide without success. Abortive attempts have l>r<-n
made by L. Varenne, J. P. Prat, P. Cillis, and T. L. Phipson 18 to prepare the gas by wet
processes analogous to those employed for chlorine by the oxidation of soln. containing
hydrofluoric acid. We now know that this is altogether a wrong line of attack. Some of
the dry processes indicated above may have furnished some fluorine ; for example, in
H. B. Dixon and H. B. Baker's experiment, silver foil in the vicinity of the uranium fluoride
was spotted with white silver fluoride ; gold foil, with yellow auric fluoride ; and platinum
foil, with chocolate platinic fluoride.

In 1834, M. Faraday 19 thought that he had obtained fluorine "in a separate
state " by electrolyzing fused fluorides, but later, he added :

I have not obtained fluorine ; my expectations, amounting to conviction, passed away
one by one when subject to rigorous examination.

This was virtually the position of the fluorine question about 1883, when H. Moissan, 20
a pupil of E. Fremy, commenced systematic work on the subject, and the reports of
the various stages of his work have been collected in his important monograph
Le fluor et ses composes (Paris, 1900). He first tried (1) The decomposition of
gaseous fluorides by sparking e.g. the fluorides of silicon, SiF 4 ; phosphorus, PF 5 ;
boron, BF 3 ; and arsenic, AsF 3 . The silicon and boron fluorides are stable. Phos-
phorus trifluoride forms the pentafluoride. The fluorine derived from phosphorus
pentafluoride reacts with the material of which the vessel is made ; similarly with
arsenic fluoride. (2) The action of platinum at a red heat on the fluorides of
phosphorus and silicon. Phosphorus pentafluoride furnishes some fluorine which
unites with the platinum of the apparatus used ; phosphorus trifluoride formed the
pentafluoride and fluo-phosphides of platinum ; silicon tetrafluoride gave no signs
of free fluorine ; H. Moissan came to the conclusion that no reaction carried out at
a high temp, was likely to be fruitful. (3) The electrolysis of arsenic trifluoride to
which some potassium hydrogen fluoride was added to make the liquid conducting ;
any fluoride given off at the anode was absorbed by the electrolyte forming arsenic

H. Moissan then tried the electrolysis of highly purified anhydrous hydrofluoric
acid, but he found, consonant with G. Gore's and M. Faraday's observations, 21 that
anhydrous hydrofluoric acid is a non-conductor of electricity. If a small quantity
of water be present, this alone is decomposed, and a large quantity of ozone is
formed. As the water is broken up, the acid becomes less and less conducting, and,
when the whole has disappeared, the anhydrous acid no longer allows a current to
pass. He obtained an acid so free from water that "a current of 3f> {nnjien-s
furnished by fifty Bunsen cells was totally stopped." The current passed readily
when fragments of dry potassium hydrogen fluoride KF.HF, were dissolved in the
acid, and a gaseous product was liberated at each electrode. Success ! The
element fluorine was isolated by Henri Moissan on June 26th, 1886, during the
electrolysis of a soln. of potassium fluoride in anhydrous hydrofluoric acid, in an
apparatus made wholly of platinum. In this way, H. Moissan solved what
H. E. Roscoe called one of the most difficult problems in modern chemistry.

While the new element possessed special properties which gave it an individuality
of its own, and a few surprises occurred during the study of some of its combinations ;
yet the harmonious analogy between the members of the halogen family fluorine,
chlorine, bromine, and iodine was fully vindicated. With fluorine in the world
of reality, chemists were unanimous in placing the newly discovered clement at the
head of the halogen family, and in that very position which had boon so long assigned
to it by presentiment or faith.



1 G. Agricola, Interpretatio Germanica vocum rei metallicce, Basil, 464, 1540.

2 A. J. Cronstedt, Mineralogie, Stockholm, 93, 1758 ; C. A. Napione, Elemenii di Mineralogia,
Turin, 373, 1797 ; F. S. Beudant, Traite elementaire de mineralogie, Paris, 2. 517, 1832 ; M. Sage,
Siemens de mineralogie docimastique, Paris, 155, 1777.

'' ,1. (!. Wallerius, Mineralogie, Berlin, 87, 1750.

4 H. Kopp, Geschichte der Chemie, Braunschweig, 3. 368, 1845.

6 A. S. Marggraff, Mem. Acad. Berlin, 3, 1768.

6 C. W. Scheele, Mem. Acad. Stockholm, (1), 33. 120, 1771 ; Opuscula chemica et physica.
Lipsse, 2. 1, 1789.

7 M. Boullanger, Experiences et observations sur le spath vitreux, oufluor spathique, Paris, 1773 ;
A. G. Monnet, Rozier's observations sur la physique, 10. 106, 1777 ; Ann. Chim. Phys., (1), 10.
42, 1791.

8 C. W. Scheele, Mem. Acad. Stockholm, (2), 1. 1, 1780 ; Opuscula chemica et physica, Lipsae,
2. 92, 1789 ; Chemical Essays, London, 1-51, 1901.

9 J. C. F. Meyer, Schr. Berlin. Ges. Naturfors., 2. 319, 1781 ; J. C. Wiegleb, CrelVs Die neuesten
Entdeckungen in der Chemie, 1. 3, 1781 ; C. F. Bucholz, ib., 3. 50, 1781 ; L. B. G. de Morveau,
Journ. Phys., 17. 216, 1781 ; M. H. Klaproth, CrelVs Ann., 5. 397, 1784 ; F. C. Achard, ib., 6.
145, 1785 ; M. Puymaurin, ib., 3. 467, 1783.

10 A. L. Lavoisier, Traite elementaire de chimie, Paris, 1. 263, 1789.

11 J. L. Gay Lussac and L. J. Thenard, Ann. Chim. Phys., (1), 69. 204, 1809.

12 A. Ampere, reprinted Ann. Chim. Phys., (6), 4. 8, 1885 ; F. D. Chattaway, Chem. News, 107.
25, 37, 1913.

13 H. Davy, Phil. Trans., 103. 263, 1813 ; 104. 62, 1814 ; Ann. Chim. Phys., (1), 88. 271, 1813.

14 G. Aime, Ann. Chim. Phys., (2), 55. 443, 1834 ; C. J. and T. Knox, Proc. Roy. Irish Acad., i.
54, 1841 ; Phil. Mag., (3), 9. 107, 1836 ; C. J. Knox, ib., (3), 16. 199, 1840 ; P. Louyet, Compt. Rend.,
23. 960, 1846 ; 24. 434, 1847 ; E. Frerny, ib., 38. 393, 1854 ; Ann. Chim. Phys., (3), 47. 5, 1856.

15 G. Gore, Phil. Trans., 160. 227, 1870 ; 161. 321, 1871 ; Chem. News, 50. 150, 1884.

16 H. Kammerer, Journ. prakt. Chem., (1), 85. 452, 1862 ; (1), 90. 191, 1863 ; A. Baudrimont,
ib., (1), 7. 447, 1836 ; L. Pfaundler, Sitzber. Akad. Wien, 46. 258, 1863 ; 0. Loew, Ber., 14. 1144,
2441, 1881 ; B. Brauner, ib., 14. 1944, 1881 ; Journ. Chem. Soc., 65. 393, 1894 ; Zeit. anorg.
Chem., 98. 38, 1916 ; O. Ruff, ib., 98. 27, 1916 ; Zeit. angew. Chem., 20. 1217, 1907.

17 0. T. Christensen, Journ. prakt. Chem., (2), 34. 41, 1886 ; A. Baudrimont, ib., (1), 7. 447,
1836 ; A. C. Oudemans, Rec. Trav. Chim. Pays-Bas, 5. Ill, 1886 ; H. Moissan, Bull. Soc. Chim.,
(3), 5. 454, 1891 ; H. B. Dixon and H. B. Baker, Private communication.

18 T. L. Phipson, Chem. News, 4. 215, 1861 ; J. P. Prat, Compt. Rend., 65. 345, 511, 1867 ;
L. Varenne, ib., 91. 989, 1880 ; P. Cillis, Zeit. Chem., 11. 660, 1868 ; G. Gore, Chem. News, 52.
15, 1885 ; E. Wedekind, Ber., 35. 2267, 1902.

19 M. Faraday, Phil. Trans., 134. 77, 1834 ; Experimental Researches in Electricity, London,
1. 227, 1849.

20 H. Moissan, Compt. Rend., 99. 655, 874, 1884; 100. 272, 1348, 1885; 101. 1490, 1885;
102. 763, 1245, 1543, 1886; 103. 202, 256, 850, 1257, 1886; 109. 637, 862, 1889; 128. 1543,
1899 ; Ann. Chim. Phys., (6), 12. 472, 1887 ; (6), 24. 224, 1891 ; Bull. Soc. Chim., (3), 5. 880,
1891 ; Les classique* de la science, 7, 1914.

21 G, Gore, Phil. Trans., 159. 189, 1869 ; M. Faraday, ib., 124. 77, 1834.

3. The Preparation of Fluorine

When an electric current is passed through a cone. aq. soln. of hydrogen chloride,
chlorine is liberated at the anode, and hydrogen at the cathode. When aq. hydro-
fluoric acid is treated in the same way, water alone is decomposed, for oxygen is
liberated at the anode, and hydrogen at the cathode. The anhydrous acid does
not conduct electricity, and it cannot therefore be electrolyzed. H. Moissan
found that if potassium fluoride be dissolved in the liquid hydrogen fluoride, the
soln. readily conducts electricity, and when etectrolyzed, hydrogen is evolved at
the cathode, and fluorine at the anode. In the first approximation, it is supposed
that the primary products of the electrolysis are potassium at the anode, fluorine
at the cathode : 2KHF 2 ==2HF+2K+F 2 . The potassium reacts with the hydrogen
fluoride reforming fluoride and liberating hydrogen : 2K+2HF=2KF-f H 2 .
The reaction is probably more complex than this, and the platinum of the electrodes
plays a part in the secondary reactions. Possibly the fluorine first forms platinum
fluoride, PtF 4 , which produces a double compound with the potassium fluoride.



This compound is considered to be the electrolyte which on decomposition forms
the two gases and a double potassium platinum fluoride which is deposited as a
black mud. This hypothesis has been devised to explain why the initial stage of
the electrolysis is irregular and jerky, and only after the lapse of an hour, when the
substances in soln. are in sufficient quantities to make the passage of the current
regular, is the evolution of fluorine regular. 0. Ruff * has shown that ammonium
fluoride can be used in place of the potassium salt.

H. Moissan first conducted the electrolysis in a U-tube made from an alloy of platinum
and iridium which is less attacked by fluorine than platinum alone. Later experiments

FIG. ] .Tube for the Electro-
lysis of Hydrofluoric Acid.

FIG. 2. Moissaii's Procass for Fluorine.

showed that a tube of copper could be employed. The copper is attacked by the fluorine,
forming a surface crust of copper fluoride which protects the tube from further action.
Electrodes of platinum iridium alloy were used at first, but later electrodes of pure platinum
were used, even though they were rather more attacked than the alloy with 10 per cent, of
iridium. The electrodes were club-shaped at one end so that they need not be renewed so
often. The positive electrode was often completely corroded during an experiment, but

the U-tube scarcely suffered at all. A copper tube is
illustrated in Fig. 1. The open ends of the tube are
closed with fluorspar stoppers ground to fit the tubes
and bored with holes which grip the electrodes. The
joints are made air-tight with lead washers and
shellac. The U-tube, during the electrolysis, is
*" surrounded

with a glass cylinder, B, into which
liquid methyl chloride is passed from a steel cylinder
via the tube A, Fig. 2. Liquid methyl chloride boils
at 23, and it escapes through an exit tube. The
fluorine is passed through a spiral platinum tube also
placed in a bath of evaporating liquid methyl chloride,
G". This cools the spiral tube down to about 50,
and condenses any gaseous hydrogen fluoride, which
might escape with the fluorine from the U-tube. The
electrolysis was carried out at a low temp, in order to
prevent the gaseous product being dil. with the vapour
of hydrogen fluoride, and also to diminish the destruc-
tive action of the fluorine on the apparatus. In his
later work, H. Moissan cooled the U-tube used for
the electrolysis by using a bath of acetone with solid
carbon dioxide in suspension. This cooled the appara-
FIG. 3. Fluorine by the Electrolysis tus down to about 80. The ternp. of the electrolysis
of Fused Alkali Hydrofluoride. vessel should not be so low that the potassium hydrogen

fluoride crystallizes out. Hence, O. Ruff and P.

Jpsen 2 preferred to cool the electrolysis vessel with a freezing mixture of calcium chloride,
and condensed the hydrogen fluoride vapours in a copper condenser C, Fig. 2, cooled with
liquid air. The fluorine which leaves the condenser (J, travels through two small platinum
tubes, 1) and E, containing lumps of sodium fluoride, which remove the least traces of
hydrogen fluoride by forming NaKIIK. A glass cylinder is placed outside each of the
two cylinders containing methyl chloride. Tim outer cylinders contain a few lumps of
calcium chloride, so as to dry the air in the vicinity of tho cold jacket, and prevent, I he


deposition of frost on the cylinders. With a current from 2G to 28 Bunsen cells in series,
and an apparatus containing from 90 to 100 grms. of anhydrous hydrofluoric acid containing
in soln. 20 to 25 grms. of potassium hydrogen, fluoride, H. Moissan obtained between two
and three litres of fluorine per hour.

C. Poulenc and M. Meslans 3 have devised a copper apparatus for the preparation of
fluorine on a large scale ; and likewise a portable laboratory apparatus, also of copper.
They substitute a perforated copper diaphragm in place of the U-tube for keeping
the two electrode products separate. The platinum anode is hollow, and is cooled
internally. G. Gallo did not get good results with this apparatus. W. L. Argo and
co-workers prepared fluorine by the electrolysis of molten potassium hydrofluoride
in an electrically heated copper vessel which served as cathode, the anode being
made of graphite. A copper diaphragm with slots was used as illustrated in Fig. 3.
The bubbles of hydrogen evolved during the electrolysis were deflected from the
interior of the diaphragm by means of a false bottom. The graphite anode was
connected with a copper terminal and insulated by a packing of powdered fluorspar
current, 10 amps., 15 volts ; temp., 240-250 ; efficiency, 70 per cent. These
co-workers also recommend sodium hydrofluoride because it is non-deliquescent ;
decomposes below the fusion temp. ; contains more available fluorine for a given
weight ; and is less expensive.


1 0. Ruff, Zeit. angew. Chem., 20. 1217, 1907 ; 0. Ruff and E. Geisel, Ber., 36. 2677, 1903.

2 O. Ruff and P. Ipsen, Ber., 36. 1177, 1904.

3 C. Poulenc and M. Meslans, Rev. Gen. Acetylene., 230, 1900 ; G. Gallo, Atti Accad. Lincei,
(5), 19. i, 200, 1910 ; W. L. Argo, P. C. Mathers, R. Hamiston, and C. 0. Anderson, Journ. Phys.
Chem., 23. 348, 1919 ; Chem. Eng., 27. 107, 1919.

4. The Properties of Fluorine

Is fluorine an element ? Since fluorine had never been previously isolated, it
remained for H. Moissan to prove that the gas he found to be liberated at the
positive pole is really fluorine. Many of its physical and chemical properties, as
will be shown later, agree with those suggested by the analogy of the fluorides with
the chlorides, bromide, and iodides. It was found impossible to account for its
properties by assuming it to be some other gas mixed with nitric acid, chlorine, or
ozone ; or that it is a hydrogen fluoride richer in fluorine than the normal hydrogen

To show the absence of hydrogen, H. Moissan allowed the gas to pass directly from the
positive pole through a tube containing red-hot iron ; any hydrogen so formed was collected
in an atm. of carbon dioxide. The latter was removed by absorption in potassium hydroxide.
ID several experiments a small bubble of gas was obtained which was air, not hydrogen.
The increase in weight of the tube containing the iron corresponded exactly with the fluorine
eq. of the hydrogen collected at the negative pole. The vapours of hydrogen fluoride were
retained by a tube filled with diy potassium fluoride. For example : In one experiment a
platinum tube containing iron increased in weight 0'138 grm. while SO'Ol c.c. of hydrogen
were collected at the negative electrode. This represents '007 12 grm. of hydrogen, and
0-00712 x 19 = 0'134 grm. of fluorine. This number is virtually the same as the weight of
fluorine actually weighed.

Fluorine at ordinary temp, is a greenish-yellow gas when viewed in layers a
metre thick ; the colour is paler and more yellow than that of chlorine. The liquid
gas is canary-yellow ; the solid is pale yellow or white. Moissan's gas has an in-
tensely irritating smell said to recall the odour of hypochlorous acid or of nitrogen
peroxide. Even a small trace of gas in the atm. acts quickly on the eyes and the
mucous membranes ; and, in contact with the skin, it causes severe burns, and
rapidly destroys the tissues. If but a slight amount is present, its smell is not


unpleasant. The relative density l of the gas (air unity) determined by H. Moissan
in 1889, by means of a platinum flask, was 1*26 ; that calculated for a diatomic gas
of at. wt. 19*5 is 1*314, and B. Braunef attributed the difference to the presence of
some atomic fluorine. H. Moissan's later results (1904) rendered B. Brauner's
hypothesis unnecessary since a density of 1*31 was obtained. The gas employed
previously is supposed to have been contaminated with a little hydrogen fluoride.
Most of the physical properties of fluorine at a low temp, have been determined by
H. Moissan himself and in conjunction with J. Dewar. 2 The sp. gr. of liquid fluorine
is 1-14 at 200, and 1*108 at its b.p. 187. The sp. vol. of the liquid is 0*9025 ;
and the mol. vol. 34*30. The capillary constant of the liquid is about onc-sixt h of
that of liquid oxygen, and seven-tenths of that of water. The coefficient of ex-
pansion 3 of the gas is 0*000304. The volume of the liquid changes one-fourteenl h
in cooling from 187 to 210. When the gas is cooled by rapidly boiling liquid
air, it condenses to a clear yellow liquid which has the boiling point 187 at 700 nun.
press. ; and the liquid forms a pale yellow solid when cooled by liquid hydrogen.
The solid has the melting point 233. The solid loses its yellow tint and becomes
white when cooled down to 252. Chlorine, bromine, sulphur, etc., likewise lose
their colour at low temp.

J. H. Gladstone's 4 estimate for the atomic refraction of fluorine for the ZMine
is 0'53; for the ^-lineO'63; and for the #-lineO*35 with the /z-formula, andO'92 and
0*84 respectively with the /i, 2 -formula. F. Swarts estimated 0*94 //a, 1*015 />, ami
0*963 Hy with the /x, 2 -formula for fluorine in sat. organic compounds ; and for
unsaturated compounds with the ethylene linkage, H a , 0*588 ; D, 0'665 ; Hy, 0*638.
The atomic dispersion is 0*022 with sat. and 0*05 with the unsaturated compounds.
J. H. Gladstone also made several estimates of the index of refraction of fluorine,
and his 1870 estimate gave 1*4 (chlorine 9*9) ; in 1885 he placed it at 1*6 ; and in
1891, he considered it to be " extremely small, in fact, less than TO." The difficulty
is due to the fact that when the magnitude of a small constant is estimated by
subtraction from two large numbers the probability of error is large. A direct
determination by C. Cuthbertson and E. B. R. Prideaux gave for the index of
refraction of fluorine for sodium light, /x=l'000195, which makes the refractivity
(p, 1) XlO 6 to be 195. The emission spectrum of fluorine has been investigated by
H. Moissan and G. Salet. 5 The last named, in 1873, compared the spectra of silicon
chloride and fluoride, and inferred that five lines in the spectrum of silicon fluoride
must be attributed to the fluorine. H. Moissan's measurements, in 1889, measured
13 lines in the red part of the spectrum. The lines of wave-length 677, 640*5, 634,
and 623 are strong ; the lines 714, 704, 691, 687*5, 685*5, 683*5 are faint ; and 749,
74C, and 734 are very faint. Liquid fluorine has no absorption spectrum when in
layers 1 cm. thick.

According to P. Pascal, fluorine is diamagnetic ; the specific magnetic suscepti-
bility is 3*447 XlO~ 7 ; and the atomic susceptibility calculated from the add it ive
law of mixtures for organic compounds is 63X10" 1 . Ionic fluorine is univalent
and negative. The decomposition voltage required to separate this element from
its compounds is I 1 75 volts. 7 The ionic velocity (transport number) 8 of fluorine
ions at 18 is 46*6, and 52'5 at 25 with a temp, coeff. of 0*0238.

Fluorine possesses special characters which place it at the head of the halogen
family. It forms certain combinations and enters into some reactions in a way
which would not be expected if the properties of the element were predicted solely
by analogy with the other members of the halogen family. From this point of
view, said H. Moissan, I' etude des composes fluores reserve encore bien des surprises.
Fluorine is the most chemically active element known. It combines additively
with most of the elements, and it usually behaves like a univalent element although
it is very prone to form double or complex compounds in which it probably exerts a
higher valency. It also acts as an oxidizing agent. In the electrolysis of manganese
and chromium salts a higher vicld of chromic acid or manganic acid is obtained in
the presence of hydrofluoric arid than in the presence of sulphuric acid. 9 Fluorine


unites explosively with hydrogen in the dark with the production of a flame with a
red border, and H. Moissan showed this by inverting a jar of hydrogen over the
fluorine delivery tube of his apparatus. The product of the action is hydrogen
fluoride which rapidly attacks the glass vessel when moisture is present, but not if
the two gases are dry. Fluorine retains its great avidity for hydrogen even at
temp, as low as 252*5 when the fluorine is solid, and the hydrogen is liquid.
H. Moissan and J. Dewar 10 broke a tube of solid fluorine in liquid hydrogen. A
violent explosion occurred which shattered to powder the glass apparatus in which
the experiment was performed. It is rather unusual for the chemical activity of
an element to persist at such a low temp. The affinity of fluorine for hydrogen is
so great that it vigorously attacks organic substances, particularly those rich in
hydrogen. The reaction is usually accompanied by the evolution of heat and light,
and the total destruction of the compound. The products of the reaction are
hydrogen fluoride, carbon, and carbon fluorides. The avidity of fluorine for hydrogen
persists at very low temp., for turpentine and anthracene may explode in contact
with fluorine at 210. Even water is vigorously attacked by fluorine. If a small
quantity of water is introduced into a tube containing fluorine, it is decomposed,
forming hydrogen fluoride and ozone ; the latter imparts an indigo-blue tinge to the
gases in the jar. By measuring the volume of oxygen liberated when fluorine
reacts with water, and measuring the exact quantity of hydrofluoric acid formed,
H. Moissan showed that equal volumes of hydrogen and fluorine form hydrogen
fluoride. If the reaction between fluorine and water be symbolized, H 2 0-f-F 2
2HF-J-0, it follows that for every volume of hydrogen collected at the negative
pole, half a volume of oxygen should be obtained. In one experiment H. Moissan
collected 26*10 c.c. of oxygen, 52*80 c.c. of hydrogen. In another experiment he
obtained 6*4 c.c. of oxygen per 12*5 c.c. of hydrogen and eq. of 24*9 c.c. of hydrogen
fluoride. Liquid fluorine does not react with water. At 200, liquid fluorine
can be volatilized from the surface of ice without reaction.

Neither oxygen nor ozone appears to react with fluorine, and no oxygen compound
of fluorine has yet been prepared. According to H. Moissan, 11 an unstable inter-
mediate compound of ozone and fluorine is possibly formed when water acts on
fluorine to form ozonized oxygen because the ozone smell does not appear until
some time after the fluorine has been passed into the water. 0. Ruff and J. Zedner
have tried the effect of heating oxygen and fluorine in the electric arc, but obtained
no signs of the formation of a compound of fluorine with oxygen or ozone, for when
the gaseous product is passed over calcium chloride (which fixes the fluorine) a
mixture is obtained quite free from fluorine. G. Gallo obtained signs of a very
unstable compound of ozone and fluorine which is explosive at 23. Liquid
oxygen dissolves fluorine, and if the temp, rises gradually, the first fraction which
volatilizes is almost pure oxygen ; the last fraction contains most of the fluorine.
If liquid air, which has stood by itself for some time, be treated with fluorine, a
precipitate is formed which is very liable to explode. H. Moissan thinks it is
probably fluorine hydrate. 12

Solid sulphur, selenium, and tellurium inflame in fluorine gas at ordinary temp. ;
sulphur burns to the hexafluoride, SF 6 . The reactivity of sulphur or selenium
with fluorine persists at 187, but tellurium is without action at this temp.
Hydrogen sulphide and sulphur dioxide also burn in the gas the former produces

Online LibraryJoseph William MellorA comprehensive treatise on inorganic and theoretical chemistry (Volume 2) → online text (page 2 of 156)