700 



the tetranitrodimetliylbenzidine may he reduced, also the end nitration 

 product obtained from these compounds. 



As these substances are practically insoluble in hydrochloric acid 

 the reaction proceeds very slowly ; the two last named compounds 

 must be boiled for a considerable time before everything has passed 

 into solution. On cooling, the lin double salts crystallise in colourless 

 scales. I removed the tin with hydrogen sulphide and on adding 

 strong hydrochloric acid to the filtrates, 1 obtained the iiydrochlorides 

 of telraminotetramethyl- and of teti*aminodimelhylbenzidine in beauti- 

 ful, small, colourless needles. 



The first product begins to darken at 240° and decomposes at 

 251°. It contains 4 mols. of hydrogen chloride and 2 mols. of water, 



Anai.^sis: Found: ' 39.47„C 6.77„H 17.57„N 



Calculaled for C\,H,.>^/).,C1, 39.8 ,. 6.6 „ 17.4 „ 



The tetraminodiinelhylbenzidine which is formed both from the 

 tetranitrodimethylbenzidine and from the end product, crystallises 

 with 4 naols. of hydrogen chloride and 1 mol. of water. 



Analysis: Found: 38.8V„C 6.4V„H 19.37,N 



Calculated for C„H„N,OCi, 38.5 „ 5.8 „ 19.3 „ 



T happened to succeed in diazotising these amino-compounds and 

 preparing from the same a number of colouring matters varying 

 in shade from red to bluish-violet, by linking them to suitable 

 substances such as the various naphthylaminosulphonic acids and 

 naphtholsulphonic acid. Some of these colouring matters exhibit the 

 property of dyeing cotton witiiout the aid of a mordant. 



Further particulars as to the compounds described in this article 

 will be published before long in the Rec. d. Trav. Chim. 



Org. Chem. Lab. University, Utrecht. 



Physics. — ''On the field of tiro spherical ji.ved centres iriYimsTRUu's 

 theory of gravitation". By J. Droste. (Communicated by 

 Prof. H. A. LoRENTz). 



(Communicated in the meeting of October 30, 1915). 



In a former communication ') I calculated the field of a single 

 spherical centre and I investigated the motion of a particle in it. 

 I now proceed to calculate the field of two fixed spherical centres 

 according to the method followed by Lorentz in calculating the 

 field of a single centre consisting of an incompressible fluid. It 



1) Vol. XVII, page 99S. 



