LM 



CHEMISTRY. 



eorrwpooding result U obtained with super- 

 nrt^t^i tulutioD*. To CO cubic centimetre* 

 of * MpenBttnted solution of sul phale of soda 

 wereBdded: 



114 



jjtjttrtw wttk ijnip uf Ufir. 100 



..___ w4r. eo (> ........................ ITT 



OtjorrtM at IT, WJ c.c. ; nperMlnrated ralpbtU 

 ofMd&.B .............................. * 



.; ilpkl of ppd, gnum>, 

 Mlarmtl wlih crtK>uau of od. ..... .......... MO 



If to 25 cubic centimetres of the supersatu- 

 rated ulpbat-of-*oda solution arp added 12.5 

 cnbic centimetres of a solution of nitrate of 

 potaua saturated in the cold, the mixture can 

 be left exposed to atmospheric dost without 

 effect Crystallization can only be induced by 

 the direct introduction of sulphato-of-soda 

 crystals of an appreciable bulk. Hence we 

 see that tbo introduction of foreign bodies acts 

 similarly with nitro-glycerine and with super- 

 saturated solutions. As regards the action of 

 temperature, by reason of the very nature of 

 the phenomena between which it is sought to 

 establish analogies, we comprehend that their 

 action most be inverse in the two cases in order 

 to give place to comparable phenomena. At 

 low temperatures the explosive power of 

 dynamite and of explosives in general de- 

 crease notably, while under the same condi- 

 tions the instability of supersaturated solutions 

 augments rapidly. A charge of 0.2 cnbic centi- 

 metre of fulminate of mercury is without action 

 OB dynamite at 75 Cent, cold. A supersat- 

 urated solution of sulphate of soda, placed in a 

 tube, rryrtallized in 89 seconds at a tempera- 

 tare of 16* to 18 Cent, while at 8 Out. 

 the crystallization was completely effected in 

 19 seconds with the same depth of liquid. A 

 like Inversion of results was again produced 

 on introducing into a supersaturated solution 

 a pulverulent body ; and if, reciprocally, the 

 silica which serves as an absorbent for nitro- 

 glycerine is replaced by any solvent wood- 

 spirit added t<> nitro-irlycenne in the pro- 

 portion of I to 4 per cent, it prevents ex- 

 plosion. bat in this cane the very nature of 

 the body I* seriously modified. On the other 

 hand, the presence of a sufficient quantity of 

 an absorbent, like silica, prevents snporsatura- 

 ; : 



AelUn if Wmttr an AW. The question of 

 poisoning by lead, dissolved in wster passing 

 through Ivsxien pipes, has recently been dis- 

 eased In the French Academy of Sciences. 

 and the chetnbu in that body are very decided 

 In the opinion that under ordinary clrrum- 

 t*nro. oothlnif i. to tie feared from that ratine. 

 Daman Mated the rwiiltn of his own , M .< ri 

 ' in which five bottles oontnining ' 



shot were partially filled with the following 

 waters respectively : Distilled water, rain-wa- 

 ter, liim-water, Ourcq-waUr. and well-water. 

 It was found that the one containing distilled 

 water showed in a very short time truces of 

 lead in solution, while the waters charged 

 more or less with calcareous salts contained 

 none. The rapidity with which pure water 

 acts upon lead is surprising, and the effect pro- 

 duced by traces of lime in preventing this re- 

 action is not leas so. It is impossible not to 

 be reminded of Schloering's observations upon 

 clay, which, in pure water, remains indefinite- 

 ly suspended, but which is precipitated by the 

 slightest trace of lime-salts. M. Dumas thinks 

 that pure water is an agent not y ( -t perfectly 

 known, and that its properties differ from 

 those of common water more than is suspect- 

 ed. On the same subject we have a note 

 from M. Belgrand, proving the innocuity of 

 lead pipes in the Paris water-service. Of the 

 public pipes there are only 8,000 metres of 

 lead out of a total of some 1,500,000 metres. 

 Tl.e branch pipes for domestic use have a 

 total length of 1,580,000 metres, but in this 

 net-work each litre of water traverses only 5 

 to 100 metres of lead, and, where the house 

 is inhabited, the water is but a short time in 

 contact with the lead. In the 3,000 metres of 

 public lead pipes the interior surface is qnito 

 smooth, and without trace of erosion, even in 

 pipes 200 years old. The branch pipes have n 

 thin adherent crust (lime, etc.) which hinders 

 the contact of water and lend. Belgrand fur- 

 ther made a series of analyses of water used 

 in dwelling-houses, and found no traces of 

 lead. His associate, M. Le Blanc, experiment- 

 ed on a longer contact of water with lead, and 

 his tables show that very pure wattr, such as 

 that from the wells of Crenelle, though pos- 

 sessing much less saline matter than Seine- 

 water, yet has the property of preserving lend 

 from oxidation during long contact. Rain- 

 water even docs not attack the lead, unless 

 it has been received after a prolonged washing 

 of the atmosphere by rains. When it has be- 

 come insensible to the action of reagents of 

 lime, it attacks the lead rapidly, like di-tiilid 

 water. Salts of lime, in the most minute 

 quantity, notably prevent the oxidation of 

 lead in contact with water. 



Fhtnolcyanitu. This new derivative of 

 phenol possesses considerable interest as hav- 

 ing many analogies with various coloring-mat- 

 tep> derived from lichens ; it is possible, also, 

 that the study of it may throw some light on 

 the constitution of indigo. It is obtained di- 

 rectly from phenol, says Dr. T. L. Phipson, by 

 dissolving the latter in alcohol, adding liquid 

 ammonia, and allowing the mixture to remain 

 for some weeks in a pnrtinlly-closed flnsk ; hut 

 in about fifteen days, when the liquid has be- 

 come a rather dark green, twice its volume of 

 water and one-quarter of its volume of om- 

 monin are added, and the mixture is left to it- 

 self for about six weeks. By that time tho 



