THE STRUCTURE O F S I T H A T E D CELLULOSE. I The Swelling and Disintegration of Ramie Cellulose in Sitrating Acids n Y F R . ~ N K DOUGLAS MILES ASD MATRICE MILBOL-RS
It has long been known that the preparation of a nitrated cotton fibre containing less than about 107 of nitrogen by nitration in a mixture of SUIphuric and nitric acids was liable to yield a disintegrated or “parchmentised” product. In the course of preparation of samples of nitrated ramie for X-ray analysis it was found impossible to obtain a product containing about 95; of nitrogen, and retaining the original fibrous structure. No matter how the composition of the acid was raried, subject to the condition of causing this degree of nitration, the material alvivnys became either friable or gelatinous. The phenomenon is of interest and it seemed desirable to know more precisely in what composition of mixed acid or of nitric acid it might be expected to occur. -1series of nitrations was therefore carried out, directed mainly to the production of cellulose nitrates containing less than I O . j c C of nitrogen. Although these substances are of considerable chemical interest they have no t,echnical importance on account of their insolubility in all solvents, and little is known of them. I t has been frequently stated that such lower nitrates are not homogeneous substances’; but it is probable that this belief has been based partly on the disintegration which is the main subject of this discussion. Experimental Materials and Methods. For the greater part of the work ramie fibre was employed, for it has the advantage of being free from the convolutions which complicate the structural examination of cotton. The material used had been purified by boiling with dilute sodiiini hydroxide and carbonate under a pressure of 6 0 lb. and by bleaching with sodium hypochlorite. I t was found by analysis t o yield o.4jyc of ash, and to have a “copper number” of 0 . 3 1 ~ and a soda solubility of 5 . 2 per cent. The nitration mixtures were made up from clear acids free from impurity other than small amounts of nitrous acid. The ramie was carefully teased out, dried for three hours at I O O ~ ,and then immersed in the acid at. 20’ for two hours, with occasional stirring, j o C.C.of acid being used for each gram of fibre. At the end of this time the fibre was deprived of acid as far as possible, submerged in cold water, washed several times with fresh water, then boiled twice with water for I + hours each time, and finally twice with water containing 0 . 0 2 7 7 ~ of sodium carbonate. For the majority of cases, in which it was not necessary to keep the sample longer than some weeks, 1 Sapojnikow: 2. ges. Schiess- und Sprengstoffe, 4, 443 (1909);Lunge and Babie: J. Am. Chem.sSoc., 23, 528 (1901). Schwalbe: “Chemie der Zellulose”, 628 (1911).
T H E STRUCTCRE O F NITRATED CELLULOSE
2599
this stabilisation was sufficient. When the fibre was greatly disintegrated by the acid it was filtered through a nitrated filter-cloth and then washed and stabilised. The estimation was carried out by a method which was in the main the same as Koehler, Macqueyrol and Jovinet’s adaptation of Devarda’s method’. This gave good agreement with the nitrometer for samples which could be analysed in both ways. It was found by special tests that the amount taken as sample for analysis was representative of the whole. Results. The compositions of the mixed acids and the percentages of nitrogen in the nitrated materials, are given in Table I. It is convenient to study the results by plotting the composition of the acid mixtures on a triangular chart (Fig. I ) . This diagram is divided broadly into three regions
FIO.I MBm. Poudres, 19, 351
(1922).
2600
FRAXK DOUGLAS MILES A S D MAL-RICE MILBOURS
by two lines which enclose an intermediate area in which lie the compositions of all mixtures which have an appreciable swelling or disintegrating effect on the fibre. The broken lines represent series of acids which give rise to certain degrees of nitration, indicated on each by the percentage of nitrogen in the nitrated product. These lines follow the same general course as these plotted by other workers' but extend the observations to lower degrees of nitration than have hitherto been systematically studied.
TABLEI No. I 2
3 4
5 6 7 8 9
%
HzSOI
____ __ __ 8.0
_-
__
I1
6.j 5.3 14.9
I2
11.7
I3 I4 15 16
20.3 26.3 23.9
17
30.5 28.8 34.6 33.2 31.8 31.5 39.4 39.3 45.1 43.2 39.0
IO
I8 I9 20 21 22
23 24 25
26 27
28 29 30 31 32
27.2
45.4
48.6 51.1 56.9 52
.o
5%
C7
HXOI 89.8 86.6
*
N 10.2
13.4
IO j
8.23 7.53
OS IG zG ,J D
8j . o
Ij.0
82.6 79 9 79.0
17.4 20. I
13 . o
9.97
I
77.8
22.2
7.22
2G
76.8 75.9 72.8 71.4
23.1 17.4 21.9 I 3 .7
5.83
0 D
6.69 90
2
6 8 .I 59.6 59.3 j8.I 54.8 49 ' 5 48.7 43.7 42 . o 40.3 38.4 38.0 36.4 35.8 35.6 31.1 30.9 30 ' 7 26.9 22.9 22 .6
20.2
7.70
4
IO.
I
20.I
9.05
14.4 I8 .o I8 .o
11.82 10.38
OS
10.45
4
.o
9.72 7.38 9.47 6.45 4.56 3 .41 9 .oo 7 .IO I O . 89 10.06 3.37
20
22.5 21 .7 24.8 27.9 30.I
22.6 24.3 19.I 21.2
30.0 23.7 20.7 22
.o
20.2
25.4
8.i4
10.18 9.44 I O .82 5 .60
2
2
2
OS 2
0
0 0 2
I
0 4
0 2
I
2.4 I
3
Sapojnikow: Z. ges. Schiess- und Sprengstoffe, 4, 441, 462 (rgog); Berl and Berkenfeld: Z. angew. Chem., 41, 130 (1928).
2601
T H E STRUCTURE O F NITRATED CELLULOSE
54 No.
HzS01
TABLE I (Continued) % % "03 Hz0 t
R N
$
HNOz 33 34 35 36 37 38 39 40 41 42 43 44
54.8 54.8 48.5 57.9 78 . o 62 . 2 55.2 54.8
67.9 53 . 5 87.4 78.6
22.4
22.8
9.06
4
21.3 20.3
23.9 31 , 2
8.43 2.18
3
17.7
24.4
17 . o
5.0
16 . o
21
16 . o 14.4 13.6
28.8 0.8
.6
1 z . j
34.0
18.5
5.is 12.04 9 I3 '
5.22
10.92 I .96
11.9
0.7
3.06
9.0 24.9 30.6
11.21
45 46
64.5
11.4 10.6
59.4
10.0
47 48
70.1
10.0
89.6
9.8
19.9 0.6
49
73.6
IO.
0
9.0 8.4
17.4
50
14.6
11.11
33.8 9.3 21.1
8 .oo
.o
8 .o 7 .o 6.9
9.38
__
I
3
OS I
D IS 0 G IB
0 D D I
5'
58.2
52
83 .i
53 54
j 2
76 . o
6.7
55 56
55.6 80 . o
j.4
17.3 9.0
D S 0 D IB D IS GB
4.5
15.5
BS
--/ I
j3
* The number refers to the figures illustrating the observed type of swelling; 0 indicates swelling; S splitting longitudinally; B fibres broken laterally; G fibres more or less
no gelatinised; D dissolved; J dissolved to a jelly.
I n the left-hand region of the diagram are found acids containing a high water content. By these the fibre is nitrated either feebly or not a t all. Ramie fibres, owing t o their collapse on drying, resemble ribbons with fairly thick walls enclosing a canal. Between crossed Nicols they display brilliant colour, uniform across the width, but varying along the length, and show extinction which is sharp, and in the usual sense "straight" also. Properly nitrated ramie containing 6y0 or less of nitrogen is very similar in these respects. The intermediate region is a band of varying width which stretches from top to bottom of the diagram and encloses two quite separate areas a t each end in which the cellulose is completely dissolved, the larger one repre-
FllhNK 1)OUOLAS MILES A N D MACRI
