N. MATERIA MEDIC A, THERAPEUTICS, AND HYGIENE. 647 



inconvenience, iVV^^s to -nr^ths of a gramme to the litre. 

 An appreciable percentage of phosphate of lime renders the 

 water unfit for domestic and industrial uses ; and for gener- 

 al purposes there should not be a greater percentage than 

 -j-y^ths to ^-gths of a gramme to the litre. Small percent- 

 ages of the chlorides generally affect water disadvantageous- 

 ly for drinking purposes. The maximum, however, should 

 be yf^tlis to yVV^is of a gramme to the litre. The pres- 

 ence of oroanic matter in waters has been considered one of 

 the principal causes of any injurious qualities they may pos- 

 sess ; to their presence being attributed the development of 

 such diseases as diarrhoea, dysentery, intermittent fever, ty- 

 phoid fever, etc. The organic residue should never amount 

 to more than yfoths to T^ths of a gramme to the litre. 

 1 B, July 6, 1878, 270. 



AESEXIC IX THE AIR OF EC QMS. 



The deleterious effects produced by the use of arsenical 

 green in paper-hangings, which have long been known, are 

 commonly attributed to the inhalation of the dust mechanic- 

 ally detached from the walls. The occurrence, however, of 

 cases of arsenical poisoning in rooms where no such mechan- 

 ical abrasion was possible has led Dr. Fleck, of Dresden, to 

 submit the question to the test of experiment. Four glass 

 jars were employed for tliis purpose. The interior of the 

 first was lined with paper covered with Schweinfiirth green, 

 a paste of potato starch being used as the adhesive material, 

 every square centimeter of surface having uj^on it fifteen 

 milligrammes of white arsenic combined in the copper salt. 

 The second jar was covered on its interior with a thick layer 

 of gelatine mixed with Schweinfiirth green, applied while 

 warm. Under the third jar was placed a capsule containing 

 Schweinfiirth green mixed with Avater to a thick paste. 

 The fourth was similarly prepared, except that white arsenic 

 was used instead of Schweinfiirth green. Each jar was 

 closed at the bottom by a glass plate, and at the top by a cork 

 carrying two glass tubes, one of which extended to the bot- 

 tom of the jar. Blue litmus papers Avere attached to the 

 corks, and the temperature was maintained at about 64 Fahr. 

 At the end of six hours the litmus paper in the fourth jar had 

 become red, that in the third jar at the end of twenty-four 



