SANGER AND BLACK. — QUANTITATIVE DETERMINATION OF ARSENIC. 303 



color of Spanish tobacco." For this compound Franceschi assumes 

 from the analysis and properties the formula AsHHg2Cl2, which he 



writes: 



-H 

 As - HgCl 

 -HgCl 



Lohmann,^^ who does not mention the results of Franceschi, finds 

 the reaction to run in a similar manner. But the red product decom- 

 posed with water, becoming black, and with such rapidity that an 

 analysis was impossible except through the decomposition products. 

 From this the formula AsHgsCla was assigned. Lohmann considers 

 that the reaction is always 



3 HgCIo + A3H3 = AsHg3Cl3 + 3 HCI, 



whether the precipitation is complete or not, and that the decomposi- 

 tion of the product depends (a) on the presence of mercuric chloride, 

 in which case arsenic and mercurous chloride are the products, or (b) 

 on absence of mercuric chloride, in which case mercury, arsenious acid, 

 and hydrochloric acid are the products. 



Partheil and Amort ^^ note the formula given by Franceschi, 

 AsHHg2Cl2, but evidently assume that it was for the yellow body (if 

 such indeed exists) and not for the red, which was clearly indicated 

 from Franceschi's paper. On this assumption and from Lohmann's 

 work, they consider that the following is the reaction for the formation 

 of the yellow body: 



2 HgClo -f AsHa = AsHHg2Cl2 -f 2 HCI 



and for the red: 



3 HgCl2 + AsHs = AsHgsCla + 3 HCI 



These reactions were given by Franceschi and by Lohmann respec- 

 tively, but both of these authors were dealing with the red body. 

 Partheil and Amort further consider these bodies to have the following 

 structure, respectively: 



12 Pharm. Zeitutig, 36, 748 and 756 (1801). 



IS Ber. d. deutsch. Chem. Gesell.,31, 594 (1898). 



