SULl'lllK, SKLENIUM, SIIJC'ON, ETC. ^i 



Erlenineyor flask ; uml this h.is Wen fuuml useful in the prerient 

 author's hihonitoiy. When cooled, the substiatuiii is in<x*uliited 

 with an organism known to he suitahle for the jiuip<jse in view, 

 and the whole is then left to stand for a day at alxtut 37' C, If 

 the substance c'ontiiin arsenic, the contents of the tube or flitsk 

 will, at the expiration of that periotl, emit a stronj( and per- 

 sistent odour of garlic. lio.^io cites, as the most energetic 

 assistant in this connection, the (presumaldy new) I'enirillium 

 hreviraitle discoveied by him on arsenical wall paper. In older 

 to be sure in the lirst experiment, the liberated vapours may Ije 

 passed into an oxidising li(piid, e.ij. permanganate solution, 

 iind examined by the Marsh test, liy tlie aid of this microbio- 

 logicjil methoil Fu. Ahua (I.) succeeded, in a case under judicial 

 investigation, in proving the presence of arsenic in a s;imple of 

 Indian meal ; then in the urine of a patient treated with 

 arsenic ; and also in illuminating gas from the Turin maiit.s, 

 the arsenical constituents being collected by passing the 

 gas through caustic potiish. In the s;ime manner, .seveml 

 hundreil sjimples of pelts were tested for arsenic (§ 157) by 

 (!(»sio (V.), ami also later on by Abha (II.). In proof of the 

 delicacy of the method, the last-named worker .stiites that, 

 whilst, with the Marsh apparatus, no arsenic could be detected 

 in a piece of hide measiuing 5 sq. cm., an unetpiivocally aflirma- 

 tive answer was obtiined bv the bioloirii'al method from a niece 

 one-liftieth the size, i.e. only 10 sq. m.ui. This metho<l has also 

 been employed, and its delicacy appreciated, by CI. MoPUUGO 

 and AuH. Ukinnek (I.) for tlie examination of colouring matters 

 used in the jtrovision industry. Samples containing not more 

 than 0.2 ni.g. of arsenious acid per 10 grams gave merely a 

 very slight, doubtful mirror in the Marsh appanxtus ; but when 

 treated in the manner proscribed by CJosio they disengaged a 

 strong odour of garlic within a few hour.s. A still more favour- 

 able opinion is expres.sed by W. Sciiolz (I.), R. Abel and P. 

 BiTrKNHEUG (I.). Hit. (Jalli-Vai.kiuo and C. Stuzvzowski (I.), 

 who found the limits of delicacy of the process correspond to 

 0.02 to 0.05 ni.g., and 0.00 1 to 0.0 1 ni.g. of arsenic respectively. 

 The reaction was not given by other metiillic poisons, such as 

 compounds of antimony, lead, and bismuth in j^irticular. Out 

 of more than forty dilVerent species of mould fungi that have 

 up to the pre.sent been examined with regard to their suit;ibility 

 for thi> method, PinirilUinn hreviraulf has proved r'(i«*i7<' pniirtjui. 

 On the other hand, A.fjierijilliis jl(iru.g — which, according to 

 II. ScuMiuT (I.), has a very powerful reducing action — ..4. iiiijtr, 

 A. iiuhfmcKit, A. funu'(/afii.<, I'enicilliuni ijlauruin, Mwor mucalo, 

 ami others, have been found iinsuiti\ble, the odtnn- of garlic 

 being either entirely ab.sent, or else njaske<l by the fusty smell 

 of the mould fungi. 



Tn view of the details given in the foregoing, it may be 



