CHEMISTRY. 



91 



apparatus for determining the sulphates con- 

 tained in wines, by which as low a proportion 

 as one half a gramme of sulphate per litre of 

 wine can be ascertained, The process requires 

 ten test-tubes placed in two parallel rows, five 

 in each row ; a pipette of 25 c.c. graduated in 

 five divisions, each of 5 c.c. ; a burette gradu- 

 ated in five divisions from 0*5 c.c. to 2*5 c.c., 

 each division consequently containing 0'5 c.c. 

 Five cubic centimetres of the wine to be tested 

 are put into each of the test-tubes of the first 

 row ; Marty's standard liquid, 10 c.c. of which 

 precipitate O'l gramme of potassium sulphate 

 per litre, is then added, to the first tube 0'5 

 c.c., to the second 1-0 c.c., and so on, till the 

 fifth tube receives 2'5 c.c. The contents of 

 the five tubes are heated and filtered respect- 

 ively into the five tubes of the second rank. 

 It is then merely needful to add a drop of the 

 standard liquid to each of the second set of 

 tubes, and to notice in which tube it produces 

 a faint turbidity. If, for instance, this turbid- 

 ity appears in number 2 and not in number 3, 

 it follows that the wine contains more than 2 

 grammes of potassium sulphate and less than 

 3 grammes. 



Mr. Charles W. Folkard, in criticising the 

 processes of analysis for the determination of 

 organic matter in potable waters, notices, as a 

 defect of them all, that since the products of 

 the decomposition of the organic matter are 

 the same as the normal constituents of rain, 

 viz., carbonic acid, ammonia, and nitric acid, 

 it is impossible to ascertain whether those sub- 

 stances were derived from contaminating bod- 

 ies, or have been dissolved by the rain in fall- 

 ing. It is possible in the oxidation method to 

 determine approximately the minimum amount 

 of contamination which has taken place since 

 the water was precipitated as rain, by deduct- 

 ing the average amount of nitrogen in water 

 falling to the earth from the total amount 

 found. But this affords no direct evidence as 

 to the fitness of the water for dietetic pur- 

 poses, because subsequent oxidation and fer- 

 mentation may have rendered it to a great 

 extent harmless. Regarding the subject in a 

 biological aspect, the effect of mere dilution is 

 hardly appreciable in disarming the germs of 

 disease of their power. A single germ in a 

 glass of water is competent to convey disease 

 to a person sufficiently debilitated. It would 

 be impossible to banish zymotic disease from 

 towns the water of which contains the dejecta 

 of persons suffering from the disease, even 

 though in the most minute quantity. The very 

 feeble would contract the complaint from the 

 water, and from them it would spread to the 

 robust around them. These germs are en- 

 dowed with a most persistent vitality, and it 

 appears that once-contaminated water is un- 

 suited for dietetic purposes. Irrigation, chem- 

 ical treatment, and filtration are alike power- 

 less to effect a real purification of sewer-con- 

 taminated water. The only way to ascertain 

 if a sample of water is fit for drinking pur- 



poses is, in Mr. Folkard's opinion, to trace it 

 to its source and see that contaminating mat- 

 ter has been excluded from the time that the 

 water fell as rain till it entered the reservoir 

 or the engine-well. 



Dr. Edmund W. Davy, of the Royal College 

 of Surgeons, Ireland, has applied a new and 

 expeditious test for the determination of ni- 

 trites in water, which is based upon the reac- 

 tion of nitrous acid or a soluble nitrite on gallic 

 acid. "When an aqueous solution of the latter 

 acid is brought in contact with a soluble nitrite, 

 the mixture, unless the amount of the latter 

 substance present be very small, will soon ac- 

 quire a yellow or yellowish-brown tint that 

 will increase in depth up to a certain point, 

 after which the color remains permanent, while 

 at the same time minute globules of gas make 

 their appearance in the mixture. If the quan- 

 tity of nitrite present is exceedingly small, the 

 reaction at the ordinary temperature will take 

 some days, but may be made almost immediate 

 by heating to the boiling-point. The depth or 

 intensity of the color produced being in direct 

 proportion to the amount of nitrite reacting 

 on the gallic acid, the quantitative determina- 

 tion of the nitrites may be conveniently ef- 

 fected by comparing the color produced with 

 that given by a standard solution containing 

 a known quantity of nitrite. With this test, 

 Dr. Davy has detected an amount of nitrite in 

 water equivalent to one part of nitrous acid in 

 twenty million parts of water. He is not pre- 

 pared to say how much more delicate it may 

 be. He considers it almost, if not quite as 

 delicate, as Griess's test, and more convenient 

 in many respects. The nitrates do not produce 

 the reaction described, and do not affect the 

 test, unless they are present in large quantities. 



IMPROVED APPARATUS. C. R. Tichborne, 

 F. R. S., describes a new form of apparatus for 

 estimating ammonia in potable waters. It 

 consists of a retort fitting air-tight into a fair- 

 ly long-necked receiver, with an India-rubber 

 stopper. To the receiver is attached a bent 

 tube proceeding from its stopper and con- 

 necting it with two bulb-tubes of a special 

 form, somewhat similar to a flat Liebig's pot- 

 ash bulb, but with two pear-shaped bulbs on 

 each side to prevent regurgitation of the fluid, 

 and three absorption-bulbs at the bottom, the 

 center one of which is provided with a glass 

 tap. The whole apparatus having been con- 

 nected, and the two bulbs filled with water 

 free from ammonia, the water to be examined 

 is poured into the retort and distilled over 

 gently. After the distillation is completed the 

 most of the ammonia, if not all, will be found 

 in the receiver, while any vapor which may 

 have escaped will be found in the first, and 

 any atmospheric ammonia which may have en- 

 tered by regurgitation, in the second bulb-tube. 



Cross and Bevan's new apparatus for deter- 

 mining melting-points consists of a small strip 

 of thin sheet-iron, having a hole at one end to 

 admit the bulb of the thermometer, fitting it 



