drying, and likewise upon boiling with water, and to determine which is the best method of drying, I made the following experiments :

I placed 6-4418 grammes of perfectly pure mercury upon a watchglass, poured distilled water over the metal, removed the water again as far as practicable (by decantation and finally by means of blotting-paper), and weighed. I found the weight to be 64412 grammes, which, after several hours' exposure to the air, were reduced to 64411 grammes. I placed these 6.4411 grammes under a bell-jar over sulphuric acid, the temperature being about 62° or 63° F. After the lapse of 24 hours the weight had not altered in the least. I introduced the 6.4411 grammes of mercury into a flask, poured a copious quantity of distilled water over it, and strongly boiled the mixture for 15 minutes. I then placed the mercury again upon the watch-glass, dried it most carefully with blotting-paper, and weighed. The weight was now 6 4402 grammes. Finding that a trace of mercury had adhered to the paper, I repeated the same experiment with the 6-4402 grammes. After 15 minutes' boiling with water, the mercury had again lost 0.0004 grm. The remaining 6-4398 grammes were exposed to the air for 6 days (in summer, during very hot weather), after which they were found to have lost only 0.0005 grm.

52. DEPORTMENT OF SULPHIDE OF MERCURY WITH SOLUTION OF POTASSA, SULPHIDE OF AMMONIUM, ETC. (to § 84, c).

a. If recently precipitated pure sulphide of mercury is boiled with pure solution of potassa, not a trace of it dissolves in that fluid; hydrochloric acid produces no precipitate, nor even the least coloration, in the filtrate.

b. If sulphide of mercury is boiled with solution of potassa, with addition of some sulphuretted hydrogen water, sulphide of ammonium, or sulphur, complete solution is effected.

c. Digestion of sulphide of mercury with sulphide of ammonium (no matter whether colorless or yellow) fails to dissolve the least trace of the mercurial sulphide; cyanide of potassium also fails to dissolve it. Hydrochloric acid produced in the sulphide of ammonium filtrate a pure white turbidity or precipitate, and in the cyanide of potassium filtrate not the least turbidity.

d. Thoroughly washed sulphide of mercury, moistened with water, suffers no alteration upon exposure to the air; at least, the fluid which I obtained by washing sulphide of mercury which had been thus exposed to the air for 24 hours, did not manifest acid reaction, nor did it contain mercury or sulphuric acid.

53. DEPORTMENT OF OXIDE OF COPPER UPON IGNITION (to § 85, b).

Pure oxide of copper (prepared from nitrate of copper) was ignited in a platinum crucible, then cooled under a bell-jar over sulphuric acid, and finally weighed. The weight was 3.542 grammes. The oxide was then most intensely ignited for 5 minutes, over a Berzelius' lamp, cooled and re-weighed, when the weight was found unaltered; the oxide was then once more ignited for 5 minutes, but with the same result.

54. DEPORTMENT OF OXIDE OF COPPER IN THE AIR (to § 85, b). A platinum crucible containing 4.3921 grammes of gently ignited oxide of copper, prepared from the nitrate, was placed for 10 minutes,

covered with the lid, in a warm room (in winter); the weight of the oxide of copper was found to have increased to 4.3939 grammes.

The oxide of copper was then intensely ignited over a spirit-lamp; after 10 minutes' standing in the covered crucible, the weight had not perceptibly increased; after 24 hours it had increased by 0·0036 grm.

55. DEPORTMENT OF SULPHIDE OF CADMIUM WITH AMMONIA, ETC. (to § 87, c).

Recently precipitated pure sulphide of cadmium was diffused through water, and the following experiments were made with the fluid.

a. A portion was digested cold with ammonia in excess, and the fluid filtered. The filtrate remained perfectly clear upon addition of hydrochloric acid.

b. Another portion was digested hot with excess of ammonia, and the fluid filtered. This filtrate likewise remained perfectly clear upon addition of hydrochloric acid.

c. Another portion was digested for some time with solution of cyanide of potassium, and the fluid filtered. This filtrate also remained perfectly clear upon addition of hydrochloric acid.

d. Another portion was digested with hydrosulphate of sulphide of ammonium, and the fluid filtered. The turbidity which hydrochloric acid imparted to this filtrate was pure white.

(A remark made by Wackenroder, in Buchner's "Repertorium der Pharmacie," xlvi. 226, induced me to make these experiments.)

56. DETERMINATION OF SODA IN SALTS WITH ORGANIC ACIDS (to $98, 4).

1.154 grm. of paratartrate of soda gave, upon intense ignition, after deduction of 0.004 grm. of charcoal, 0.63 grm. of Na O, CO,, which corresponds to 0.3698 of Na O = 32.05 per cent. (calculated 32·14 per cent.); this gives 99.7 instead of 100.

57. DETERMINATION OF BARYTA BY PRECIPITATION WITH CARBONATE OF AMMONIA (to § 101, 2, a).

0.7553 grm. of pure ignited chloride of barium was precipitated according to the directions of § 101, 2, a; the precipitate of Ba O, CO, weighed 0-7142 grm., which corresponds to 0.554719 of Ba O = 73·44′ per cent. (100 parts of Ba Cl ought to have given 73.59 parts). The result accordingly was 99.79 instead of 100.

2

58. DETERMINATION OF BARYTA IN ORGANIC SALTS (to § 101, 2, b). 0-686 grm. of paratartrate of baryta [2 (Ba O, R) + 5 aq], treated according to the directions of § 101, 2, b, gave 0.408 grm. of carbonate of baryta = 0.3169 of Ba O = 46.20 per cent. (calculated 46:38 per cent.) which gives 99.61 instead of 100.

59. DETERMINATION OF STRONTIA AS SULPHATE OF STRONTIA (to § 102, 1, a).

a. An aqueous solution of 1.2398 grm. of Sr Cl was precipitated with SO, in excess, and the precipitated sulphate of strontia washed with water. It weighed 1-4113 grm., which corresponds to 0.795408 grm. of Sr 0 = 64.15 per cent. (calculated 65.38 per cent.); this gives 98.12 instead of 100.

b. 1.1510 grm. of SrO, CO, was dissolved in hydrochloric acid in excess, the solution diluted, and then precipitated with SO,; the precipitated Sr O, S O, was washed with water; it weighed 1.4024 grm. = 0·79039 Sr O 68.68 per cent. (calculated 70.07 per cent.); this gives 98-02 instead of 100.

=

60. DETERMINATION OF STRONTIA AS SULPHATE, WITH CORRECTION (to § 102, 1).

The filtrate obtained in the experiment described 59, b, weighed 190-84 grammes. According to experiment No. 21, 11,862 parts of water containing sulphuric acid dissolve 1 part of sulphate of strontia. 190-84 grammes of the filtrate contain therefore 0.0161 grm. of that salt in solution. The washing water weighed 63-61 grammes. According to experiment No. 20, 6,895 parts of water dissolve 1 part of Sr O, SO, ; 63.61 grammes of washing water contain therefore 0·0092 grm.

the

Adding 00161 and 0.0092 grm. to the 14024 grm. of precipitated sulphate of strontia, we find the total amount = 1.4277 grm., which corresponds to 0.80465 of Sr O = 69-91 per cent. in Sr O, CO, (calculated 70-07 per cent.); this gives 99-77 instead of 100.

61. DETERMINATION OF STRONTIA AS CARBONATE OF STRONTIA (to § 102, 2).

1.3104 of chloride of strontium, precipitated according to the directions of § 102, 2, gave 1-2204 grm. of Sr O, CO,, containing 0.8551831 of Sr 065.26 per cent. (calculated 65.38), which gives 99.82 instead of 100.

62. DETERMINATION OF LIME AS SULPHATE OF LIME, BY PRECIPITATION (to § 103, 1, a).

(In the experiments Nos. 62 to 65, and No. 67, chemically pure airdried carbonate of lime was used, in a portion of which the amount of anhydrous carbonate had been determined by very cautious heating. 0.7647 grm. of the heated carbonate left 0.7581 grm., which weight remained unaltered upon further (extremely gentle) ignition of the carbonate; the air-dried carbonate contains accordingly 55.516 per cent. of lime.)

1.186 grm. of the air-dried carbonate of lime was dissolved in hydrochloric acid, and the solution precipitated with sulphuric acid and alcohol (see § 103, 1, a). The precipitated sulphate of lime weighed 1.5949 grm., containing 0.65598 of Ca O=5531 per cent. calculated 55-51), which gives 99.64 instead of 100.

63. DETERMINATION OF Ca O AS Ca O, CO2, BY PRECIPITATION WITH CARBONATE OF AMMONIA AND WASHING THE PRECIPITATE WITH PURE WATER (to § 103, 2, a).

A hydrochloric acid solution of 1·1437 grm. of the air-dried carbonate of lime of 62, gave upon precipitation with carbonate of ammonia (§ 103, 2, a), 1.1243 grm. of anhydrous carbonate of lime, corresponding to 0-629608 of Ca O=5505 per cent. (calculated 55.51 per cent.) which gives 99.17 instead of 100.

64. DETERMINATION OF Ca O AS Ca O, CO,, BY PRECIPITATION WITH OXALATE OF AMMONIA FROM ALKALINE SOLUTION (to § 103, 2, b, a).

11734 grm. of the air-dried carbonate of lime of 62, dissolved in hydrochloric acid, and treated as stated § 103, 2, b, a, gave 1·1632 grm.

of Ca O, CO, (re-action not alkaline), containing 0-651392 of CaO = 55.513 per cent. (calculated 55-516 per cent.), which gives 99.99 instead of 100.

65. DETERMINATION OF LIME AS OXALATE (to § 103, 2, b, a).

0.857 grm. of the air-dried carbonate of lime of 62 were dissolved in hydrochloric acid; the solution was precipitated with oxalate of ammonia and ammonia, the precipitate washed, and then dried at 212° F. until the weight remained constant. The precipitate (Ca O, O + aq) weighed 1-2461 grm., containing 0.477879 of Ca O=5576 per cent. (calculated 55.516 per cent.), which gives 100-45 instead of 100.

66. VOLUMETRICAL DETERMINATION OF LIME PRECIPITATED AS OXALATE (to § 103, 2, b, a).

Six portions, of 10 c.c. each, were taken of a solution of pure chloride of calcium; in 2 portions the lime was determined in the gravimetrical way (by precipitation with oxalate of ammonia, and weighing as Ca O, CO); in two by the alkalimetrical method, and in two by precipitation with oxalate of ammonia, and estimation of the oxalic acid in the precipitate by solution of permanganate of potassa. The following were the results obtained :—

67, DETERMINATION OF Ca O AS Ca O, CO, BY PRECIPITATION AS Ca O, Ō FROM ACID SOLUTION (to § 103, 2, b, ß).

0-857 grm. of the dry carbonate of lime of 62, dissolved in hydrochloric acid and precipitated from this solution according to the directions of § 103, 2, b, f, gave 0.8476 grm. of carbonate of lime (which did not manifest alkaline re-action, and the weight of which did not vary in the least upon evaporation with carbonate of ammonia), containing 0-474656 of Ca O=55-39 per cent. (calculated 55.51), which gives 99.78 instead of 100.

68. DETERMINATION OF MAGNESIA AS 2 MgO, PO, (to § 104, 2).

a. A solution of 1.0587 grm. of pure anhydrous sulphate of magnesia in water, precipitated according to § 104, 2, gave 0.9834 of pyrophosphate of magnesia, containing 0.3533944 of magnesia = 33.38 per cent. (calculated 33-35 per cent.), which gives 100-09 instead of 100.

=

b. 0.9672 grm. of sulphate of magnesia gave 0-8974 2 MgO, PO, 33.34 per cent. of Mg O (calculated 33.35 per cent.), which gives 99-97 instead of 100.

69. PRECIPITATION OF ACETATE OF ZINC BY SULPHURETTED HYDROGEN (to § 108, b).

a. A solution of pure acetate of zinc was treated with sulphuretted hydrogen in excess, the mixture allowed to stand at rest for some time, and then filtered. The filtrate was mixed with ammonia; it remained perfectly clear at first, and even after long standing a few hardly visible flakes only had separated.

b. A solution of acetate of zinc to which a tolerably large amount of

acetic acid had been added previously to the precipitation with sulphuretted hydrogen, showed exactly the same deportment.

70. DETERMINATION OF MERCURY IN THE METALLIC STATE, IN THE HUMID WAY, BY MEANS OF PROTOCHLORIDE OF TIN (to § 118, 1, 6).

2.01 grammes of chloride of mercury gave 1 465 grm. of metallic mercury72.88 per cent. (calculated 73.83 per cent.), which gives 98-71 instead of 100 (Schaffner).

71. DETERMINATION OF COPPER BY PRECIPITATION WITH ZINC IN A PLATINUM DISH (to § 119, 2).

30.882 grammes of pure sulphate of copper were dissolved in water to 250 c.c.; 10 c.c. of the solution contained accordingly 0.31387 grm. of metallic copper.

a. 10 c.c., precipitated with zinc in a platinum dish, gave 0.3140 = 100.06 instead of 100.

b. In a second experiment 10 c.c. gave 0·3138 = 100.

72. DETERMINATION of Copper AS SULPHO-SUBCYANIDE (to § 119, 3). 0.5965 grm. of pure sulphate of copper was dissolved in a little water, and, after addition of an excess of sulphurous acid, precipitated with sulphocyanide of potassium. The well-washed precipitate, dried at 212°F., weighed 0-2893, corresponding to 0.1892 Cu O=3172 per cent. As sulphate of copper corresponds to 31.83 per cent., this gives 99-66 instead of 100.

73. DETERMINATion of Copper by DE HAEN'S METHOD (to § 119, c). Four portions, of 10 c.c. each, of a solution of sulphate of copper, containing 0.0254 grm. of metallic copper in 10 c.c. of solution, were severally mixed with iodide of potassium, then with 50 c.c. of a solution of sulphurous acid (50 c.c. coresponding to 12.94 c.c. of iodine solution). After addition of starch paste, iodine solution was added until the fluid appeared blue.

This required,

In a, 4·09
b, 3.95
c, 4.06
d, 3.95

As 100 c.c. of iodine solution contained 0.58043 grm. of iodine, this gives

For a, 0.0256 C uinstead of 0·0254

Another experiment, made with 100 c.c. of the same solution of sulphate of copper, gave 0.2606 instead of 0.254 of copper. Ammonia having been added to 10 c.c. of the solution of sulphate of copper, then hydrochloric acid in slight excess, 34 and 35 c.c. of iodine solution were required instead of 4 c.c., a proof that considerably more iodine had separated than corresponded to the oxide of

copper.