removal of air from the conventional piggy, and ( 2 ) static charges. Use of piggies with two openings to permit rapid xiid complete Ausliing provided a ready ineans for renioving air. Increased use of forceps to reduce cont:tcts between dry bag and piggy and introduction of a Staticniaster minimized clifficulties due to static charges. For example, a soda-lime piggy with tn.0 openings fitted with hollowground sotlalime caps wit'h the improved technique gave the following data: calculated decrease in weight (air to nitrogen) about 0.2 nig.; found, 0.2 mg. with a range between 0.18 and 0.21 nig. Results obtained using the douldeopening piggy with ground glass stoppers are shown as S o . 3 in Table I. The data compare favorably with results by the conventional method. Typical duplicate results are given in Table I1 for seven diffcrcnt types of solid pyrophoric saniplcs of unknown composition. Thest: niaterials a-ere spontaneously flammable when exposed to the atmosphere for only a fevi seconds. Some were heterogeneous mixtures. Considering the nature of the samples, the average deviations were low enough to indicat'e the apparently successful use of the proposed method for analyses of pyrophoric compounds. The modified procedure described for pyrophoric solids also has been used for analyses of unstable liquid samples. Hypodermic syringes of 1-nil. volumr equipped with 2-inch KO. 27 gag(' needles have heen used to inject the
Table Ill. Analytical Data for Hygroscopic Compounds Found, Wt. yc~ Calcd , Wt Yc --~ _ _ SCiniplc> ._~ _ _ _ _ _ . Sanlpl(. Sue, l l g C' H C H Urea 21 9 '10 (i 6 7 20 1 ti7 11 t i 10 3 ti8 38.4 9.7 7.8 :38. i Ethylene glycol 9.7 38.3 %i 14.4
samples int,o 2-inch lengths of glass coapillary pipets 0.3 to 0.5 mm. in internal diameter and 5 mni. in outside diameter, sealed a t one end. The pipets can be handled easily with forceps \\-ithout loss of sample or contamination. The new procedure appears equally rvcll suited for analyzing hygroscopic substarices;. This is illustrated by the data shown in Table I11 obtained on duplicate analyses of technical grade urea and ethylene glycol. A few experiments were made using piggies equipped x i t h caps of Teflon tet'rafluoroethylene resin and Alathon polycthylene resin. It was felt that these plastic caps might give a better nonlubricated seal than the glass stoppers. Tvelve analyses of acetanilide gave averages of 715% for carbon and 6.7yo for hydrogen, with a standard deviation of 0.21 and 0.12%, respectively. The principal difficulty with use of the plastic caps was traced to static charges acquired during sampling and to variable moisture adsorption during weighing. Piggies made of uranium glass also were tried as a possihlc means for elimi-
-
nating static problem.. These were not as effectivp as the Staticmaster. The success of the proposed method depends on the skill of the analyst. The procedure is straightforward, however, and capable nontechnical operatorq can be trained quickly for routine nnalyses. LITERATURE CITED
Belcher, R., Goulden, R., Mikrocheml'e 36-37, 679 (1951). Burgess, G. K., ('Standard Densit'! and Volumetric Tables," 6th ed., Bur. Standards Circ. 19 (1924). Clark, T. J., Conn, P. K . , Hein, R. E., Chemist Analust 44, 55 (1955). Fischer, F. O., ANAL. CHEN.21, 827 (1949). Franklin, A. J., Voltz, S. E., Zhid., 27, 865 (1955). Xiederl, J. B., Xiederl, V., "Micromethods of Quantitative Organic. Analysis," 2nd ed., \Gley, Sei\York, 1942. Truett, K . L., Johnson, D. R . . Cheni. Eng. iyezcs 35, 52 (Oct. 21, 1957). RECEIVED for review Kovenibrr 6, 1957. r\ccepted March 11, 1958, Delawarc \-alley Regional Meeting, ACS, Febriia: \ 16, 1956.
171. Methy le ned initra m ine (Med ina ) JOHN KRC, Jr. Armour Research Foundation of Illinois Institute of Technology, Chicago 16, Ill. H
C R \TAL ~ JIORPHOLOG~
Cr\qtal Pvstcm. Orthorliomhic. Structural Formula for Methylenedinitramine
T
wo modifications of methylenedini-
tramine have been observed. Tlica stable modification, methylenedinitrxmine I, has been obtained from solution and from fusion; methyleiiedinitraminp I1 has been obtained from fusion only. Xodificntion I1 is very unstable n ith respect to modification I. Excellent crystals of mrthyleneriinitranline I can he obtained by recryqtallization on a macro scale from a saturated 9 to 1 ethylene dichloridr-ieopropy1 alcohol solution (Figure 1 ) . Figurc 2 is an orthographic projection of R tvpical tahlct of methylenrdinitraniine I.
OPTICAL PR0Pl:RTIEi
Rcfrartiw indiws (,XI3 A , : 23" C'.).
l'orm ant1 Hahit. Tcedles and rods elongated along c and plates and tahlets lying on brach:, pinacoid 010 shoniiig prism { 1101, brachydonie (0111, anti hip) raniid { 111 }. Axial Ratio. n:b:c = 0.800: 1: O 449. Interfacial Angles (Polar). 010 A 011 = 65.8"; 011 A 0 7 1 = 48.4'; 010A 110 = 51.4"; 1 l O A l l b = 77.2". Tn-inning Plane. 101.
a = 1.372 I. 0.002. p = 1.384 0.002. y = 1.598 0.002.
X-R.41 DIFFRACTIOX Da~a
CRI.
Cell Dimensions. u = 9.06 A : b = 11.33 -4.; c = 5.09 A . Formula Keights per Cell. 4 (4.01 calcthted from s-raj data). Formula Weight. 136.1. Density. 1.735 (flotation); 1 .72(9) (x-ray); 1.74 (value olitainetl from 11. R Tonilinson, Jr.).
*
*
Optic Axial Angles (5893 A . , 25' C.). 2H = 94". 21' = 89' (calculated from p and 2 H ) ; 21- = 88.5" (calculated from a . 6 . and r'i.
j5ispers:lbn. r > u; very strong. Optic A4xialPlane. 001. Sign of Double Refraction. Pohitiw'. Acute Risectris. y = b. I;:stinction. I'arnllcl and syninictri-
Molecular Refraction ( R ) (5893 A ; 25" C,). && = 1.585. R (calcd.) = 26.6 (using K = 9.94 for K202) ; R (obsd.) = 26.3. FVSIOX DATA. Afet'hyleneclinitraminc melts 17-ith considerable decomposition. Deconiposition in fusion preparations can be limited by rapid heating to slightly ahore the melting point folVOL. 30, NO. 7, JULY 1958
1301
C
C
I
I
4
114.2-
li -b
e
Figure 1. Crystals of methylenedinitramine I from 9 to 1 ethylene dichloride-isopropyl alcohol
131.6-
b A Figure 2. Orthographic projection of typical tablet of methylenedinitromine I
Figure 3. fusion
Methylenedinitromine I from
lowed by irnmnlinte cooling. Picric arid and othcr sul)stances affrct thr rtLte of thermal decomposition ( 1 ) . TIIF melt tends to superi.ool unless serdrd or suhjeetcd to mechaniral shock. Two modifications have bcen ohserved from fusion. The stable form, methylenedinitraminr I, crystallizcs as long rods of high birefringence (r'g ' 1 nre 3). Methylenedinitramine I1 can he obtained by suprrrooling the melt to approximately GO" C. and then tapping the corcrglass to initiate crystallization (Figure 4). These polymorphs are readily distingnishcd by conoscopic observation, since form I1 is uniaxial and optically negative. Form I1 often transforms to form I spontaneously. The I pseudomorphs of I1 (Figure 5) show large areas of uniform orientation which give good interference figures. The transformation I1 I is extremely rapid; the transformation I -+ I1 h a s not been observed. The melting points for forms I and I1 are somewhat uncertain because of thermal decomposition dnring beating. McCrone, by an extrapolation technique, has estimated the true melting point of form I to be 106.5" C. Ordinary fnsion techniqnes have indicated the melting point for form I to he slightly above 104.5" C. and for form I1 to he 98-100" C.
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1302
ANALYTICAL CHEMISTRY
Figure 5. Methylenedinitromine I pseudomorphs of methylenedinitramine II ACKNOWLEDGMENl
Figure
4.
Methylenedinitramine
from fusion ~
d
7.61 7.08 5.97 5.GG 4.80 4.GG 4.51 4.19 4.13 3.7i
3.49 3.38 3.23 2.91 a . 8:3 2.71
Principal Lines I/I, d 2 2.6G 7 2.60 2 2.52 ti 2.48 5 2.39 3 2.35 5 2.32 1 2.25 10 2.21 9 2.li 9 2.14 2.Oi 5 7 2.02 8 1.983 3 1.9:M 1 1,'JO'J
I/I, 1 3 G 3 G G
G 2 5
5 5 5 2 1 2 5
II
Thr meth?lenrdinitraminp was supplied hy Arthur D. Little, Inc. Donald G. Grahar conducted an extensive fusion investigation of methylenedinitmmine on the research program; the fusion data here presented are taken from his reported s o r k . An acknowledgment is due to Irene Corvin, who determined the powder x-ray spacings and intensities. LITERATURE CITED
( 1 ) Tobin, hl. C., Fowler, J. P., Hoffman,
H. A,, Seuer, C. W.,J . Am.
Chetii.
Sac. 76, 3249 (1954).
CONTRIBUTIONS of crvstallomanhic data to be published in A N ~ L Y T I.CHEMISTRY C~ should I)P sent to IT.C. McCrone, 500 East 3:M St., Chicago 16, Ill. Work performed under an nereement (Subcontract No. 13) between ?he Arm& Rerenrrlr Foundation of Illinois Institute of Tvhnologg and Arthur D.Little, Inc., Cnmbridge 42, Mnsa., under The Department of The Armv. Ordnnnre Corns. Contmrt
