Simple detection of adamsite based on substitution-type reactions

 

Science & Military 1/2007 

                                  Expert papers

 

 

 

 

 

63

 

 

SIMPLE DETECTION OF ADAMSITE  

 

BASED ON SUBSTITUTION-TYPE REACTIONS 

 

Vladimír PITSCHMANN, Emil HALÁMEK, Zbyněk KOBLIHA  

 

Abstract: Simple detection of adamsite (irritating warfare agent) in air is described. Two different methods using detector 

tubes based on substitution-type reactions  were developed. The first method is based on electrophilic reaction of adamsite 

with sodium nitrite in acidic solution which results in red nitroso or isonitroso derivate. The second method is based on 

nucleophilic reaction of adamsite with ammonium thiocyanate, affording a yellow product. The detection limit for 

adamsite in air is 0.5 µg for the first described method and 5 µg for the second. Visual evaluation of detector tubes is 

based on intensity of color developed on the indication layer.  

 

Keywords: Adamsite, detector tubes, sodium nitrite, thiocyanates. 

 

 

1.  INTRODUCTION 

 

Adamsite [10-chloro-5,10-dihydrophenarsazine, 

code labeling DM] is a warfare agent of the first 

generation, with irritating effect on the upper 

respiratory tract (for selected properties see Tab. 1).  

 

Tab. 1 Some selected properties of adamsite [1] 

Parameter Value 

CAS Number 

578-94-9 

Molecular weight 

277.54 

Structural formula 

 

 

 

 

 

 

 

Boiling point, °C 

410  

Melting point, °C 

195 

Volatility, mg.m

-3

   19 300 (0 °C), 26 000 (20 °C),  

72 500 (25 °C) 

Solubility 

acetone, furfural, hexane  

(insoluble in water) 

ICt

50

, mg.min.m

-3

 

22 – 150 

LCt

50

, mg.min.m

-3

  11 000 – 35 000 

 

The first compound of this type is 10-bromo-

5,10-dihydrophenarsazine, prepared in 1913 at 

Bayer works in Germany. Adamsite itself was 

synthesized two years later by German chemist 

Heinrich Wieland and at the end of World War I 

independently developed by a team of American 

chemists at Illinois University, headed by Roger 

Adams who suggested its possible military use. 

During the World War II, its non-nitrogen analogue 

excelsior (5-chloro-10-methylacridarsine) was 

introduced in Germany. Six thousand one hundred 

tons of adamsite have been stockpiled by the Soviet 

Union, 300 t by the U.S.A. and 3 700 t by  Germany. 

In March  1939, the  Czechoslovak Army  possessed 

one ton of adamsite. At present, this substance is 

subject to the Chemical Weapons Convention. 

Only scarce data on the military use of adamsite 

are at disposal. It was probably first deployed by 

Italian troops already before the end of World War I. 

It was used by British intervention forces during the 

Russian civil war and by the American Army in 

Vietnam. In all these cases adamsite proved to be an 

insidious and very effective warfare agent. It is also 

known that for its incapacitating effect adamsite was 

used by police forces as riot controlling agent. At 

present, it may be misused by terrorists. Thus, e.g., 

an information was disclosed about plans of some 

militant Islamic groups to use adamsite against 

selected embassies and state buildings in Belgium 

[2]. For this reason, investigation on chemical 

analysis of adamsite and structurally similar 

compounds cannot be underestimated. 

The practically only warfare state of adamsite is 

a toxic smoke capable of attacking efficiently the 

upper respiratory tract. This fact significantly limits 

the potentialities of technical means for detection of 

adamsite in air, in which also detection tubes play an 

unsubstitutable role. As regards the reaction 

principles, only a few functional variants of 

detection tubes are known. A simplest device 

contains glass wool for effective trapping of the 

aerosol, and an ampoule filled with sulfuric acid 

which with adamsite affords red coloration of 

unknown composition [3]. A similar reaction is also 

produced by action of formic acid (on heating) and 

perchloric acid which gives a pink colored product 

[4].  This  system  is  little  selective  and  therefore               

a detection tube has been developed that contains an 

ampoule with mercury(I) nitrate solution in 

concentrated sulfuric acid. The presence of adamsite 

manifests itself by a characteristic green product of 

unknown composition. A detection tube based on 

this principle has been introduced in the 

Czechoslovak Army (labeled by two white stripes) 

and   even   today a similar  device  is offered  by the 

As

N

H

Cl

 

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Russian Krismas company under specification IT-

15-30 [5]. Recently, a tube for detection of adamsite 

(and CR) has been described in the literature that 

contains silica gel impregnated with 4-chloro-5,7-

dinitrobenzofurazane [6].  Another suitable reaction 

is based on formation of red sodium salt of the 

nitration product. Adamsite is first nitrated with 

concentrated nitric acid and the formed nitro 

derivative is then treated with concentrated solution 

of sodium hydroxide to give the red sodium salt [7]. 

This reaction has also been utilized for colorimetric 

determination of adamsite at 530 nm [8] but its use 

in a detection tube has not been described. Of less 

used reactions, one may mention the reaction of 

adamsite with HI under formation of diphenylamine 

which is separated by distillation and proved e.g. by 

blue coloration on reaction with nitrates in 

concentrated sulfuric acid [9].   

The aim of the present study is to describe the 

preparation, properties and use of two types of 

detection tubes for detection of adamsite in air, 

based on electrophilic or nucleophilic substitution 

reactions affording colorimetrically (visually) 

evaluated colored products.  

 

 

2.  EXPERIMENTAL 

 

2.1  Chemicals and instruments 

 

     The  indicator  packings  and  detection  solutions 

were prepared using the following chemicals: 

ammonium thiocyanate, sodium nitrite, hydrochloric 

acid 35% (all p.a., Sigma – Aldrich), and anhydrous 

ethanol (Riedel-de Haën). The detection solution for 

the reference tubes was prepared with mercury(I) 

nitrate and 96% sulfuric acid (p.a., Sigma-Aldrich).  

     The employed silica gel (Grace, Germany), had 

particle size 0.5-0.7 mm, specific surface 200 m

2

.g

-1

 

and 120 % sorption capacity (H

2

O). The coating 

tubes, sealing elements and other mechanical 

components were furnished by the Tejas company 

(Jablonec, Czech Republic). 

     The detector tubes were tested using 10-chloro-

5,10-dihydrophenarsazine (NBC Defence Institute, 

University of Defence, Brno) of 96.3 % purity, as 

checked by classical iodometric method [8].    

 

2.2  Procedures 

 

Preparation of detection tubes with sodium nitrite 

 

     The detector tube contained an indication packing 

(layer) and a glass ampoule with detection solution. 

The indication layer consisted of silica gel which 

had been purified by boiling with dilute hydrochloric 

acid, washing with distilled water until the washings  

 

 

were neutral, and which was finally activated by 

heating at 130 °C. 

     The purified silica gel (100 g) was impregnated 

with 110 ml of 1% aqueous solution of sodium 

nitrite. The mixture was dried, first on air until the 

material became loose and then in a drying box at 90 

to 110 °C for 2 hours.      

    

 

     The thus-obtained milky white indication packing 

was poured into a glass tube to form 10 mm high 

layer and fixed by polyethylene starlets and a 

polyamide net. Finally, a glass ampoule 

containing 20% hydrochloric acid was inserted and 

the tube was hermetically flame-sealed. Detector 

tubes construction – see Figure 1.  

 

 

 

 

 

Fig. 1  Construction of detector tubes 

 

 

Preparation of detection tubes with thiocyanates 

 

     The detector tube contained a carrier and a glass 

ampoule with detection solution. Activated purified 

silica gel was employed as the carrier; the detection 

solution consisted of 5% ammonium thiocyanate 

solution in ethanol. Other construction elements 

were the same as described for detector based on 

sodium nitrite. 

 

Preparation of reference detector tubes 

 

The reference detector tube contained a carrier 

and a glass ampoule with detection solution. 

Activated purified silica gel was employed as the 

carrier; the detection solution consisted of 0.1% 

solution of mercury(I) nitrate in concentrated 

sulfuric acid. The remaining construction elements 

were the same as described for the newly devised 

detectors.  

 

Testing of detection tubes  

 

The detector tube was opened by breaking both 

sealed ends of the glass body and 20 µl of an acetone 

solution of adamsite of concentration 5, 25, 50, 150, 

250, 500 and 1500 µg.ml

-1 

was applied on the 

indication layer using a micropipette. Then, 1 dm

3

 of 

uncontaminated air was pumped through the layer 

using a manual air pump Universal 86 (Kavalier 

Votice, Czech Republic). The ampoule was crushed 

with a metal spike and the detection solution was 

thoroughly shaken down onto the carrier. The 

change in coloration of the indication layer (carrier) 

was evaluated visually. 

 

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3.  RESULTS AND DISCUSSION 

 

In the search for suitable color reactions of 

compounds structurally close to adamsite we made 

use of the known fact that polyvinylcarbazole [10] 

or indole [11] in an acidic medium afford deeply 

colored nitroso products on reaction with nitrite 

ions. A similar reaction also takes place with 

adamsite. The devised detector tube is based on 

formation of an orange to red colored product, 

probably a nitroso or isonitroso derivative, formed in 

an electrophilic substitution reaction of adamsite 

with nitrous acid arising by treatment of sodium 

nitrite with hydrochloric acid:  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Some irritants of the group of aromatic arsenic 

compounds (eg diphenylchlorarsane) react with 

sodium thiocyanate under formation of colored 

substances [12]. With the mentioned nucleophilic 

reagent, adamsite affords a yellow product, probably 

phenarsazine thiocyanate. The probable reaction 

course may be represented by the following reaction 

scheme:  

 

As

N

H

Cl

NH

4

SCN

As

N

H

SCN

NH

4

Cl

+

+

 

Both the devised substitution reactions take place 

in the detector tubes within wide range of reaction 

conditions. In the case of the nitrosation reaction that 

takes place in the presence of acids, the ampoule 

with 20% hydrochloric acid ensures sufficient 

stability of the reaction medium. The reaction of 

adamsite with thiocyanates requires no special 

adjustment of reaction conditions. The high rate of 

both the substitution reaction types makes it possible 

to practically immediately evaluate the color  change  

 

 

of indication layers in the detection tube. The arising 

coloration is stable. 

The detection limit for the sodium nitrite method 

amounts to 0.5 µg of adamsite, for the ammonium 

thiocyanate method it is 5 µg. The results obtained 

(Tab. 2) can be interpreted so that for taking 1 dm

3

 

sample of contaminated air, under assumption of 

ideal trapping on the carrier, the detection limit for 

adamsite aerosol will reach 0.5 

mg.m

-3

  and            

5 mg.m

-3  

for the respective methods. In the 

reference tube, silica gel instead of glass wool was 

employed as the carrier to ensure comparable 

reaction conditions.  

 

Tab. 2  Results   of   tests   with  detector   tubes   for  

detection of adamsite  

Coloration of detector 

DM 

(µg) 

NaNO

2

 NH

4

SCN Reference 

   

0.1 no 

no 

light 

orange 

0.5 

light yellow 

no orange 

1 yellow 

no 

yellow-green 

3 yellow 

no 

brow-green 

5 

deep yellow 

light yellow 

green-brown 

10 orange 

yellow 

 

deep 

green 

30 

deep orange 

deep yellow 

deep green 

 

     This change results in variable coloration of the 

indication packing. As detection limit for the 

reference tube we may regard 1 µg of adamsite 

which gives rise to still perceivable green coloration. 

The orange coloration at lower concentrations has to 

be ascribed to the action of concentrated sulfuric 

acid alone.  

The course and results of the tests are not 

influenced by harmful substances, commonly 

present in the atmosphere. The sodium nitrite 

detector tube may exhibit a color response in the 

presence of some aromatic amines or hydroxy 

compounds. Thus, e.g., with phenol it shows a red 

coloration as the result of the Liebermann reaction 

[13]. Substitution reactions similar to those of 

adamsite are not known for any of the known 

warfare agents (except for diphenylchlorarsane) or 

other compound of military significance. 

All the devised reagents, used as detection 

solutions or immobilized on a carrier, are stable. 

This makes possible a production of detector tubes 

of  long lifetime and usability.  

 

4.  CONCLUSION 

 

The proposed detector tubes are suitable primarly 

for chemical detector CHP-71, which belongs to 

standard equipment of the combined and special 

chemical units of Czech and Slovak military. The 

detector   tubes    can   also   be  used  in  new  semi- 

As

N

H

Cl

NaNO

2

+

+ HCl

As

N

H

Cl

As

N

Cl

NO

NaCl

+

+ H

2

O

N

OH

 

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automatic chemical detector CHP-5, which recently 

became a part of standard equipment of the Czech 

military. 

 

 

 

References 

 

[1] STŘEDA, L., HALÁMEK, E.,  KOBLIHA, Z.: 

Bojové chemické látky. 1. vyd. Praha: Státní 

úřad pro jadernou bezpečnost, 2004, s. 84. ISBN 

80-239-3102-4.  

[2]  On the street.   ASA   Newsletter, 2003,  vol. 96,  

 p. 

15. 

[3] Zjišťování látek otravných. Praha: Správa  civil- 

 

ní obrany, 1954, s. 39, 62.  

[4]  PITSCHMANN,     V.,      HALÁMEK,         E.,   

 

TUŠAROVÁ, I., KOBLIHA, Z.: Oritest, Pra-

ha. Činidlo pro testování alkaloidů.   CZ   15428 

 

U1. Int. Cl. G 01 N 21/78. 2005. 

[5]  ZOLOTOV,    YU.      A., IVANOV,   V.      M., 

AMELIN, V. G.: Chemical Test Methods of 

Analysis. 1-st ed. Amsterdam: Elsevier, 

2002, pp. 248, 268. ISBN: 0-444-50261-0. 

[6] EVGEN´EV, M.  I., GARMONOV,  S. YU., 

BELOV, 

P. E., TSEKHMISTER, V .I., 

DRUZHININ, A. .A: Test Method for the 

Determination of  Toxic Irritants in Air. J. Anal. 

 

Chem., 2003, vol. 58, p. 485.  

[7] FRANKE,  S.: Lehrbuch der Militärchemie. 

Band 2. 2. Auflage. Berlin: Militärverlag der 

DDR, 1977, s. 344. 

[8] FRANKE,  S.: Lehrbuch der Militärchemie. 

Band 2. 2. Auflage. Berlin: Militärverlag der 

DDR, 1977, s. 349.  

[9] TOMEČEK, 

I., MATOUŠEK, 

J.: Analýza 

 

bojových otravných látek. 1. vyd. Praha:  SNP, 

1961, s. 99. 

[10] 

ABE,  S.: The color reaction of polyvinyl-        

carbazole with nitrogen dioxide and its 

application  for  the  detection of  nitrogen 

dioxide. Chem. Lett., 1977, pp. 237-240. 

[11] ANDONOVSKI, B. S., STOJKOVIČ,  G. M.: 

Spectrophotometry study of the reaction of 

indole with nitrite ions in hydrochloric acid.   

Bulletin of  the Chemists and Technologists of  

 

Macedonia, 2002, vol. 21, pp. 177-185. 

[12] SARTORI, M.: Die Chemie der Kampfstoffe.  

       Braunschweig: Friedr. Vieweg & Sohn, 1935,  

       s. 220. 

[13] 

FRAENKL,  

M., SVOBODOVÁ, 

 D., 

GASPARIČ, J.: A critical investigation of the 

Liebermann colour test. Microchim. Acta, 1986, 

vol. 90, pp. 367-386. 

 

 

 

doc. Ing. Vladimír PITSCHMANN, CSc. 

1) 

prof. Ing. Emil HALÁMEK, CSc. 

2) 

prof. Ing. Zbyněk KOBLIHA, CSc. 

2) 

1) 

Oritest spol. s r.o. 

   Staropramenní 17 

   150 00 Praha 

   Česká republika 

   E-mail: [e-mail] 

2) 

Univerzita obrany Brno 

   Ústav OPZHN 

   Sídliště Víta Nejedlého 

   682 03 Vyškov 

   Česká republika 

   E-mail: [e-mail] 

                [e-mail]