Subtracting the weight of the dish from the weight of dish and ash gives the weight of the mineral matter, which was dissclved along with the

sugar.

Add the weight of this mineral matter to the weight of the insoluble mineral matter and we have the total mineral matter.

Rittenhausen's Method.

Weigh out 10 or 20 c. c. of milk, dilute to twenty times its original volume, and add to it 4.5 or 9 c. c. of acetate or of sulphate of copper.

The acetate should contain 50 grms. of the salt per litre, the sulphate 63.5 grms. per litre. Immediately after the addition of copper, just enough caustic alkali is added to decompose the copper salt, but must not be added in excess, for this would dissolve the precipitated casein copper. The clear fluid is now decanted, the precipitate of copper, protein substances, and fat thoroughly washed with water and brought upon a filter. The filtrate and washings contain all the milk sugar, which may be determined with Fehling's solution.

The precipitate is broken up with a platinum spatula and washed with absolute alcohol and then with ether, until all the fat has been removed. The last traces of ether are then removed with alcohol and the residue dried over sulphuric acid. The ethereal solution is distilled and fat residue dried and weighed. The copper, etc., residue is weighed, heated to one hundred and twenty-five degrees for one or two hours and then to redness, whereby the albumen is burned off and the amount determined on weighing the residue. Water and total solids are determined in the usual manner with sand.

The following is an outline of the method pursued by Dr. Dechan and T. Maben, and copied from October number of The Analyst for 1884:

The total solids are determined separately in a shallow vessel with a flat bottom, the quantity of milk taken being 5 grms. The vessel is large enough to allow the residue to form in a thin film, and there is no difficulty in obtaining weighings which correspond with the weight of the fat and non-fat solids. This, therefore, forms a good check, being for all practical purposes a duplicate analysis.

For the fat, and solids not fat, 10 grms. are weighed into a capsule capable of holding double that quantity. This is placed on an open waterbath and the milk stirred repeatedly during evaporation. By this means a granular residue is obtained, which, when reduced to powder, is in the best possible condition for the extraction of the fat. This we accomplish with ether, by means of one of the many forms of extraction apparatus modeled on the principle of Soxhlet's tube. The fat and solids not fat are determined separately, both being dried till they lose not more than 0.001 grm. in an hour.

The conclusions reached by Dechan and Maben are as follows:

1. That the total solids be determined separately, and, if time be specified, that the quantity in weight of milk and the shape and size of the evaporating vessel be stated.

2. That the solids for fat extraction be obtained in a fine granular condition by repeated stirring during evaporation. Using ten grms. of milk, the time necessary for this need not exceed one and one half, or, at the very utmost, two hours.

3. That the fat be extracted in some such apparatus as we have recommended; time allowed for extraction to be from one and one half to two hours.

4. That all the constituents be weighed, viz: Total solids, fat; solids not fat, and ash. This gives practically duplicate analyses and forms a valuable check on the accuracy of the results.

The methods of Mathew A. Adams has elicited some attention from English analysts.

Mr. Adams uses a carefully prepared and weighed coil of blotting-paper to absorb the milk taken for analysis, dries the coil, and then, by the use of ether or benzole, dissolves the fat from the residue left upon the coil, evaporates the solvent, and determines the fat by weighing.

He then carefully dries and weighs the coil, and from the data now furnished him determines the solids not fat. Among other advantages claimed for this method, are the following:

First--That the fat is completely extracted.

Second-That the last trace of water is removed from the solids not fat. The following is the method of analysis used by myself:

In a wide, shallow, flat-bottomed, weighed, plantinum dish, weigh about five grammes of milk (much more than this amount renders complete dessication and extraction of fat slow and tedious, while, on the other hand, a much smaller quantity is not desirable as a basis for determination of ash). Place the dish, with its contents, over a water-bath and evaporate to a solid residue; from this residue expel the remaining water by heating in a hotair oven at 100° C. I have usually allowed the residue to remain in the oven about an hour, and then weighed every fifteen or twenty minutes until two consecutive weighings gave the same result, when the milk solids were considered completely dry. From the weight of the dish and milk solids, substract the weight of the dish, and divide the remainder by the weight of the milk taken. This gives us the per cent. of total solids.

The dish is now filled with ether or benzole and allowed to stand under a bell-jar for two hours or more; the liquid is then decanted off from the residue, which is repeatedly rinsed with the same solvent, dried and weighed. This process is repeated until constant weight is obtained and the fat completely extracted. The residue now left in the dish is the solids not fat, whereas, the loss of weight sustained represents the amount of fat. From the data the percentage of fats and solids not fat are calculated.

The dish containing the solids not fat is now heated to dull redness until thoroughly decarbonized and a white or gray ash is obtained, cool and weigh; substract weight of dish and we have the weight of mineral matter.

For the estimation of lactose weigh out fifteen or twenty grammes of milk, dilute with equal volume of water, acidulate with five or six drops of acetic acid, and warm to coagulate the casein.

After cooling, filter and wash curd repeatedly to remove all traces of lactose, dilute, filtrate, including washings to one fourth or one half of a litre, and estimate lactose by use of Fehlings fluid.

i Casein is estimated indirectly by substracting lactose and ash from solids not fat.

This method is recommended by Prof. Stephen P. Sharpless in a pamphlet on milk analysis, written by himself; and many duplicate analyses have been made by him to establish the accuracy of the method, at least so far as regards the power of obtaining concordant results.

The following are the results of two duplicate analyses made by Prof. Sharpless:

A second sample of milk supposed to be adulterated, gave the following

Duplicate analyses, made by myself, gave results as follows:

I have made several other duplicate analyses, but the memoranda of all of them are lost, so that this is all that I am now able to give.

With regard to the use of ether and benzole, in my experience, I have found that ether dissolves the fat more quick y than benzole, but under ordinary conditions of analysis I do not think that in the end the action is any more complete than benzole.

Lactometer.

The lactometer is an instrument used for indicating the specific gravity of milk. At a temperature of 60° F. it indicates a specific gravity between 1000 and 10348. The stem of the lactometer is graduated from 0 to 120; O indicates the specific gravity of water, viz: 1000; the 100 mark indicates a specific gravity of 1029, specific gravity below which pure milk rarely