SCIENCE 



NEW YORK, JULY 7, 1S93. 



HYDRAZOIC ACID : A NEW FORM OF APPARATUS FOR 

 ITS PREPARATION; ITS PHYSIOLOGICAL ACTION. 



BY CYBIL G. HOPKINS, SOUTH DAKOTA AGRICULTURAL COLLEGE, 

 BROOKINGS, SOUTH DAKOTA. 



Most of the text-books on the subject of chemistry in use at 

 the present time still recognize but one compound of hydrogen 

 and nitrogen, viz., ammonia. There are, however, now known 

 to science, several compounds of these two elements. Of these 

 the most important are ammonia, NHj ; hydrazolc acid, HN3 ; and 

 hydrazine, N^H^. There is a remarkable difference in the prop- 

 erties of the first two substances. Ammonia, the volatile alkali, 

 has very strong basic properties, uniting directly with acids to 

 form the ammonium salts. Only with the strongest basic ele- 

 ments does it act like an acid, forming sodium amide, NaNHj, 

 with sodium, and potassium amide, KNHj, with potassium. 



Hydrazoic acid, on the contrary, is a comparatively strong 

 acid. Being a binary compound of hydrogen and nitrogen, it 

 might well be called hydronitrio acid, after the analogy of hydro- 

 chloric acid, hydrobromic acid, etc. Its structural formula is 

 represented thus: — 



N 



N 



\N 



Its hydrogen r.tom is readily replaced by metals and radicals, 

 the salts of hydrazoic acid being thus formed. The ammonium 

 salt contains only hydrogen and nitrogen, and is formed by direct 

 union of ammonia and hydrazoic acid : — 



NHs -f HN3 = NH4N3 = N^H^. 

 Hydrazoic acid also rmites with hydrazine, another compound 

 of hydrogen and nitrogen, possessing the formula 



NH3 



NjHi, or 1 . 



NHj 



This substance, hydrazine, or diamine, as it is sometimes called, 



CH3 

 bears to ammonia the same relation that ethane, CjHj, or | , 



CHs 

 CcH3 

 bears to marsh gas, CH4; or that diphenyl, | , bears to benzine, 



C5H5 

 CjHg. Like ammonia, hydrazine possesses strong basic proper- 

 ties. With hydrazoic acid it forms two compounds by direct ad- 

 dition: — 



NHs NH3N3 



I -t-HN3= I =-^,B.„ 



NHa NH^ 



and 



NH3 NH3N3 



I +2HN3=| =N3H,. 



NHs NHsNs 



Thus we have at least six compounds of the elements hydrogen 

 and nitrogen, their general formulas being: — 



NH3, N2H4, NjH^, N5H5, NsHe, and HNs. 

 Heretofore hydrazoic acid and its derivatives have been made 

 only by reactions' of organic chemistry; but within the past few 

 months a method has been devised by Wislecenus^ by which the 

 acid is made entirely from inorganic substances. This is done by 

 first treating molten metallic sodium (or potassium) with dry 

 ammonia gas, and then treating the sodium amide thus formed 



1 Berichte der deutsch. Chem. Gesellaohatt (Curtlus), xxlll., 3023; xslv., 

 33i5. Ibid (Noetlng and Grandmongln), xxlv., 2546. 

 a Ibid, xsv., SOW. 



with dry nitrous oxide. The sodium salt of hydrazoic acid is 

 thus formed ; and, by treating this with dilute sulphuric acid, 

 the hydrazoic acid itself is liberated, and may then be distilled off 

 with water, thus giving a dilute aqueous solution. 



Wislecenus performed the operation in a small porcelain boat 

 within a glass tube. The porcelain is strongly attacked by the 

 sodium compounds, and the yield of hydrazoic acid which Wisle- 

 cenus obtained was nearly 50 per cent of the theoretical amount, 

 and, besides, only a small quantity of the acid (about one-half a 

 gramme) could be made at a time. 



These objections to the apparatus used by Wislecenus induced 

 the author to seek for a better form of apparatus with which to 

 prepare the acid. 



A cylindrical copper air-bath was selected, which was provided 

 with two mica windows placed opposite each other, through 

 which any operation that was carried on within the bath could 

 be easily observed. The bath was about fifteen centimetres from 

 top to bottom and of about an equal diameter. The cover was of 

 heavy asbestos board. In the centre of this a large circular 

 opening was made, through which a glass beaker of 750 cubic 

 centimetres capacity was inserted into the bath until its rim 

 rested upon the asbestos board, the bottom of the beaker not 

 being allowed to touch the bottom of the bath. A small quan- 

 tity of clean sand was placed in the bottom of the beaker, and 

 upon this a small iron sand-bath, hemispherical in shape, and 

 having a capacity of 100 cubic centimetres. The mouth of the 

 beaker was closed with a large flat cork, provided with three holes. 

 Through the central hole passes a glass tube which reaches a 

 little way into the iron dish, and through which the gases are 

 conducted into the apparatus. The second hole carries a short 

 exit tube, and the third a thermometer. 



Neither the metallic sodium nor the compounds formed have 

 any action upon the iron dish, and the reactions which take place 

 in the dish can be readily observed through the mica windows of 

 the air-bath and the glass beaker. 



The ammonia gas was obtained by gently heating on a water- 

 bath a flask containing strong ammonia water, and the nitrous 

 oxide by the decomiiosition of ammonium nitrate by heat. The 

 gases were dried as directed by Wislecenus, by passing them over 

 soda-lime and solid potassium hydroxide. 



To perform the operation 25 grammes of metallic sodium were 

 placed in the iron dish, the temperature of the bath raised to 

 300'' — 360° C, and dry ammonia gas conducted in and deliv- 

 ered just above the surface of the molten sodium. The specific 

 gravity of sodium being less than that of the amide formed, the 

 metal floats on the surface until the action is finished. The reac- 

 tion is represented by the equation : — 



NH3 -1- Na = Na NH, -|- H. 



When the globules of sodium had all disappeared, the nitrous 

 oxide was substituted for the ammonia, and the temperature of 

 the- bath lowered to 230" — 250" C. Two reactions now take 

 place. The two atoms of hydrogen in the sodium amide are re- 

 placed by the bivalent group, N,, contained in the nitrous oxide, 

 the hydrogen and oxygen uniting to form water. This then 

 reacts with a second molecule of sodium amide, forming sodium 

 hydroxide and ammonia : — 



NaNHs -I- NjO = (NaNNj = NaN,) + H^O, and 

 NaNHa + HjO = NaOH + NH,. 



The sodium compounds have a strong tendency to creep over 

 the edge of the iron dish as fast as they are formed; but they only 

 fall upon the sand in the bottom of the beaker, from which they 

 are readily dissolved out by water. 



When the odor of ammonia ceases to be given off, the reaction 

 is complete. The apparatus was allowed to cool, the mixture of 

 sodium hydroxide and the sodium salt of hydrazoic acid was dis- 



