THE ANALYST. APRIL 1894. THE COMPOSITION OF MILK AND MILK PRODUCTS. BY H. DROOP RICHMOND. Read at the Meeting Februarg 7th 1894. THIS paper is a continuation of the annual reports of the work done in the laboratory of the Aylesbury Dairy Company. The results obtained during 1893 are given in the present communication. (For previous reports see ANALYST vii. 53 ; viii. 33; ix. 56 ; x. 67 ; xi. 66 ; xii. 39 ; xiii 46; xiv. 69 ; xv. 44; xvi. 61 ; xvii. 62 ; and xviii. 50.) The total number of samples analyzed during the year 1893 was 30,504; this is I large increase the numbers having gradually advanced year by year from 8,817 in 1881 when the company's iaboraiory wa8 first established. 28,487 samples of milk. 1,121 9 cream. 624 , separated and skimmed milk. 13 7 buttermilk.122 I butter. 91 9 water. 46 , sundry articles. Of the milk samples 14,643 were taken from the railway churns on their arrival at the Company's chief dep6t. The bulk of this is distributed with the least possible delay to the customers a certain portion being however utilized for the productio 74 THE ANALYST. of cream etc. To control the men employed in delivering the milk a further 11,479 samples were taken before during and after delivery and analyzed compara-tively. I n the following table the average monthly results of these analyses are given. The samples taken on arrival before and during delivery were almost exclu-sively analyzed by estimating the total solids and specific gravity and calculating the fat. A large portion of those taken at commencement of and after delivery were, however examined by the Leffmann-Beam method and the total solids calculated.The agreement is equally good between the different series. No cases in which the milk had been tampered with were found. AVERAGE COMPOSITION OF MILK DURING 1893. ~ 1893. Month. January February March April June July August September October November December Average May ~~ ~~ On Arrival. / I . Sp. Gr. 1.0321 1.0321 1.0320 1.0319 1.0319 1.0316 1,0311 1.0314. 1.0316 1.0317 1,0321 1.0321 -_ 1.0318 Tot. Sol. 12-68 12.58 12.52 12.53 12-46 12.37 12.41 Fat. 3.85 3.76 3.73 3.75 3.70 3-70 3.83 12-54 ~ 3.89 12.80 1 4.06 13.20 1 4.39 12.94 1 4.08 12.68 1 3.91 13.09 i 4.21 -?.n. F 8.83 8.82 8.79 8.78 8-76 8.67 8.58 8.65 8.74 8.81 8.88 8.86 8.77 .~ Before Delivery. Tot. Sol. 12.50 12.46 12.46 12.45 12.42 12.30 12.31 12.46 12-64 12.93 12.90 12-77 At 'Om- During )f Delivery. nencement Delivery. Tot. Sol. I Tot. Sol. I 12.60 ' 12.68 12.56 12.57 12.52 12.52 12.40 ~ 12.45 12.37 12.40 12.29 12.35 12.47 12.63 12.94 12.91 12.72 12.31 12-35 12-44 12.62 13-03 12.96 12.76 12.55 12.56 i 12.58 After Delivery. Tot. Sol. 12.71 12.64 12.60 12.55 12.61 12.44 12.39 12.48 12.66 12.99 19-90 12.73 --12.64 After the abnormal summer of 1893 one would have naturally expected to find that the milk this year was of poorer quality than usual ; and it will probabIy be a matter of surprise that the yearly average of total solids is but 0.03 per cent.lower than that of last year the amount of fat being absolutelyidentical with that of the past two years, the difference being only in the solids-not-fat. During the months of June July and August the solids-not-fat were distinctly below the average and this seems to have been the only effect of the season on the composition of milk. I have already shown (ANALYST xviii. 270) that by careful examination it has been possible in many cases to distinguish between abnormal and watered samples and have nothing further to add here on this subject. I may say that when the mixed milk of a whole farm has been examined during 1893 in but one instance has the fat fallen below 3.0 per cent., and in this one case it was 2.99 per cent.The experience of this year has gone to show that the Society's limit for fat is well fixed. The highest percentages of total solids and fat occurred in October and the lowest in June THE ANALYST. 75 . . I 47.5 .______-.____ Cream samples were taken before and during delivery. The average of the results is given in the following table : 47.9 ~ ~ ~ __ -AVERAGE AMOUNT or FAT IN CREAM IIURIAG 1893. Month. January . . February . hfarch . . April . . May . I . . * June J uly . . August . . September October . . November . . December . . Before Delivery. 45.0 45.5 46.3 47.3 48.4 48.8 46.7 47.3 50.8 49.8 46.8 47.3 After Delivery.45.5 46.0 46.5 48.4 48.9 48.4 47-2 47.5 50.8 50.9 47.4 47.7 Considering the difficulty of drawing average samples of cream of such richness, The average composition of clotted cream (51 samples) was as follows : the agreernent between the two series is satisfactory. Average. Water . . . . 30.77 Fat . . . . 61.49 Ash . . . . -60 Solids-not -fat . . . 7.74 These figures do not greatly differ from those found in former years. The bulk of samples of separated milk contained less than -3 per cent. of fat ; in The lowest amount of fat contained in rare instances it contained above -4 per cent. skimmed inilk was -04 per cent. Butter had the following composition : French butter fresh ; 35 samples. Water . . 15.53 to 11.12 ; average 13.65 Salt .. *25 !) *05 ) -13 Fat . I . . 87.06 ,) 83.27 ) 84.99 Solids-not -fat . 1.86 , *86 , 1.36 Reichert-Wollny figure 27.5 , 32.3 , 30.2 French butter salt ; 28 samples. Water . . 13-49 ,) 9-17 ) ) 11.61 Fat . . 88-07 ,) 82-74 ,) 85.08 Salt . . . 2.95 ,) 1-08 ) 1.86 Solids-not-fat . 4.83 ) ) 2.32 , 3.31 Reichert-Wollny figure 27.5 , 33.0 ) ) 29. 76 THE ANALYST. English butter salt; 43 samples. Water . . . 15.33 to 10.28 average 12.76 Fat . . 87.24 , 82.25 ) 84.53 Solids-not-fat . 3-94 , 1.16 , 2.71 Salt . . 3.31 , -59 , 1.90 Reichert-Wollny figure 21.6 , 32.3 , 28.1 Water . . . . 14.36 , 13.10 , 13.64 Fat . . 83.52 , 82.02 ,) 82.96 Solids-not-fat . 3.62 , 3.19 , 3-40 Salt . . 2.36 , 2.07 ,) 2-19 Reichert-Wollny figure 29.5 , 31.2 , 30.5 was churned at Bayswater and duplicate determinations were made.not however lower than has been found by Vieth Mayer Lupton and others, For the discussion of the amount of water in butter see ANALYST xx. 16. The Leffmann-Beam glycerol method has been exclusively used during 1893 for the determination of the volatile acids. I t will be noticed this year that French butters give a higher Reichert-Wollny figure than English butters ; reference to previous reports will show that this has been invariably the case. A sample of butter which had been kept for two years exposed to air and light, and which Dr. Vieth had found when fresh to require 29.9 C.C. :n alkali to neutralize the volatile acids from 5 grammes took 29.5 C.C. FG alkali. Another sample received by Dr.Vieth from the German Commission on Butter Analysis in 1888 and which he has on several occasions analyzed (see ANALYST xiv. 148 ; xv. 173)) took 33.9 C.C. TT alkali as against 32.0 C.C. originally. A sample of milk was skimmed in three portions-Le. after six hours’ standing, eighteen hours and twenty-four hours. The last very small quantity of cream on being churned into butter took identically the same amount of alkali 26.5 c.c., as the earlier portions. I t seems that the larger and smaller globules of fat do not differ chemically . The specific gravity of every sample of milk which comes into the laboratory is taken. This determination is of the greatest value and when taken with a lacto-meter as is our practice next to no trouble. Lactometers which can be read to the fourth place of decimals with a little practice are now made which require only 2 oz.or 4 oz. of milk. I t must however be borne in mind that the specific gravity of milk cannot be accurately taken until the expiration of some hours after milking, for until this time as Vieth has pointed out (ANALYST xiv. 71) Recknagel’s phenomenon is still going on. The following figures were obtained : Swedish butter salt; 3 samples. One sample of English butter gave a Reichert-Wollny figure of 21.6 C.C. ; this This figure is An opportunity occurred this year of studying this. Specific gravity 12 hours after milking . . 1.0310 9 J ) 3& 9 ) 7 9 . . 1.0322 9 , 18 9 $ 7 9 ) . . 1.0325 This rise in specific gravity must not be confounded with a similar rise in the observed specific gravity shown when frothy milk is allowed to stand; it is quit THE ANALYST.77 independent and is due to some change in the dissolved constituents of the milk. When milked air-bubbles are always mixed with the milk but these rise to the top in the course of an hour or less leaving a very little froth on the top which is very persistent and must be removed before taking the specific gravity ; occasionally it happens that a sample for analysis contains much froth and great care must then be exercised in taking the specific gravity. For very exact determinations of the specific gravity a small (10 c.c.) Sprengel tube must be used; a bottle is inadmissible as there is not time for the temperature to become equal throughout before some of the cream separates.With the Sprengel tube uniformity of temperature is reached in a few minutes and accuracy to .0001 is easily attained. All exact determinations of total solids have been done by the asbestos method and the results have been most satisfactory. Macfarlane's chrysotile (ANALYST xviii. 73) method has also been studied and the statement in his paper, that this method gives lower results than drying in a basin confirmed. It seemed to me that as no figures were given as to whether the chrysotile could be dried to constant weight and whether it gave anything to ether it was desirable to examine into this point : Weight of tube and chrysotile after 20 hours at 100" C. The tube was then wetted with 10 C.C. of water and dried : Weight of tube and chrysotile after 19 hours at 100" C.. 16.266 9 9 9 , 5 , more . . 16.263 . 16.2675 3 ) 9 9 , 24 , more . . 16.264 9 9 $ 9 9 17 9 9 . . 16.269 It was then extracted with ether and on drying . . 16.263 No ether extract whatever was obtained. The weighings though not entirely satisfactory show that chrysotiIe can be dried and re-dried to a fairly constant weight. I n three milks the total solids were estimated : Chrysotile method . 5 hours at 100" C. 13.00 9 9 9 20 , 7 12.63 12.85 $ 9 9 25 , 9 12.63 12-82 12-77 Asbestos method in basin 9 ) 1 9 13-23 13.21 13.09 Difference . . a60 -39 -32 I n each case the chrysotile method was lower and the residue was of a brown Fat was also estimated by the chrysotile method and compared with the Adams . colour while it was white in the asbestos method.method : Chrysotile method-Fat direct weighing . 4.12 4-28 3.88 , by difference . 4.13 4.27 3.91 Adadls metho; . . . . 4.08 4.17 4.06 . . The tubes were percolated with ether about six times; in the first two cases a There does not As the total solid determination does not compare with the methods used in little chrysotile had run thrcjugh which makes the results high. seem to be much difference between the two methods 78 THE ANALYST. England and moreover is probably low as the residue is brown this method is not likely to be adopted here. Numerous comparisons between the Adams and Werner-Schmid methods were again made this year ; the Werner-Schniid averaged ~ 0 3 higher than the Adams and had a probable error of j=*O41 the probable error of the Adams being A-027.shows that the Werner-Schrnid method is good enough for ordinary work; it has not however in my hands proved such a very rapid method an hour and a half being the least time in which a satisfactory estimation can be performed. I find that it is necessary to allow the tube in which the dissolved milk and ether have been shaken up to stand at Zeast ten minutes before drawing off the ether as before that time the ether contains minute water globules visible to the naked eye, and more easily seen with a magnifying glass. I have found it very difficult to prevent a slight loss of ether on taking out the stopper of the tube. I have now quite discarded this method for either the Leffmann-Beam centrifugal method in case a rapid determination is wanted or the Adams method where accuracy is a desideratum.I n doing an accurate Adams estimation attention to the following points is necessary : i. The ether must be anhydrous (dried over calcium chloride and distilled is suE cien t). ji. Schleicher and Schiill's fat free papers should be used and one should be extracted without any milk on it in a flask used as a tare for the others. iii. Four or five hours' extraction is necessary. iv. The coils must be well dried before extraction. This Neglect of the first second and fourth precautions causes the results to be too high and as one or more of these had been neglected in the data from which the formula of Hehner and myself and my modified formula were calculated I thought it desirable to calculate a new formula.The determinations were made as follows : Specific gravity. By a Sprengel tube frequently tared at 15.55' C. (deter-mined by a Kew standardized thermometer read to &' C.). Total solids. Asbestos method. Fat. The results are given in two series. Adams method using the precautions enumerated. I n Series I. all determinations of total solids and fat are means of well agreeing duplicates; in Series 11. some of the specific gravities were taken with a lactometer and many of the total solid and fat determinations were not done in duplicate. Series I. extends over an entire year and the results axe arranged in order of date ; the importance of this will be realized later : SERIES I. T. F. F. calc. Difference.Remarks. G. D.- G. 1. 34.9 33.7 9.27 -28 -35 +so7 1st Peri od 2. 30.8 29.9 12.75 4.10 4.08 - *02 Y , 3. 33.5 32.4 12.88 3.70 3.65 - *05 ? I 4. 32.0 31.0 12.83 3.85 3.91 +*06 9 5. 31.7 30.75 13.09 4-13 4.18 + -05 I THE ANALYST. 79 G. 6. 32-2 7. 26.0 8. 32.3 9. 32.5 10. 14.1 11. 31.7 12. 32.0 13. 31.8 14. 32.6 15. 25.8 16. 32.3 17. 324 18. 32.0 19. 29-4 20. 29.9 21. 61-4 22. 36.0 23. 32.8 24. 32.7 25. 32.6 26. 32.7 27 32.5 28. 23.4 29. 33.2 30. 32.4 31. 32.7 32. 32.6 33. 32.8 34. 32.6 35. 32.4 36. 32.5 37. 32.5 38. 31-8 39. 32-4 40. 32.3 41. 32.0 42. 30.9 43. 32.1 44. 32.0 45. 32.9 46. 31-6 47. 31.6 48. 32.1 49. 32-0 50. 32.1 51. 32.1 52. 32.6 53. 32.4 54. 31.0 55.31.5 56. 314 G. D. 31.2 25 *35 31.3 31 -5 13.9 30-75 31.0 30.8 31-55 25-15 31 *3 31.4 31.0 28.55 29.05 57.85 34-75 31.75 31.65 31.55 31.65 31.5 22.85 32.15 31.4 31-65 31.55 31.75 31-55 31.4 31.5 31.5 30.8 31.4 31.3 31.0 29-95 31.1 31.0 31.85 30.65 30.65 31.1 31.0 31.1 31.1 31.55 31.4 30.05 30.55 30.45 - T. 12.56 10-17 12.96 12.75 5.57 12-25 12.48 13.74 13.04 10.06 12.52 12.58 13.09 12-06 12-64 20.84 11.68 12.44 12-42 12.41 11-91 12.32 9.82 11.86 12.59 12.51 12.58 12-62 12.29 12.25 12.30 12-30 12-59 11-91 12.27 12.64 11.34 12.60 12.16 11.97 12.51 12-62 12.39 12-42 12-14 12.06 11.74 11 -73 11 -95 12.36 12.30 F.3.65 2.92 3.92 3-72 1-56 3.56 3-66 4-64 3.99 2.93 3.60 3.65 4.06 3-78 4.13 4.73 2.06 3-48 3.46 3.51 3-01 3-46 3-21 2.92 3.64 3-61 3-70 3-67 3-41 3.49 3-46 3-52 3-76 3.14 3-48 3.80 2.88 3.65 3.35 2.85 3.67 3.77 3-40 3.44 3-21 3.19 3.00 2.99 3.31 3.51 3.52 F. calc. 3.64 2.93 3.96 3.74 1.60 3-48 3.63 4-72 3.97 2.88 3.59 3.62 4-12 3-82 4.18 4.61 2.13 3 *42 3 *43 3.44 3 *OO 3.38 3.18 2.86 3.63 3.50 3.58 3-58 3.34 3-35 3.37 3.37 3.76 3.05 3.38 3.75 2.90 3.70 3.35 3-01 3-72 3-81 3.52 3.58 3.32 3.25 2.88 2-92 3-38 3.62 3.59 Difference. Remarke. - -01 1st Period.+ -01 1 + ~ 0 4 1 1 + *02 1 1 + 604 1 9 - -08 1 1 - *03 1Y + a08 Y 1 - -02 1 7 - *05 1 1 - -01 1 1 - a 0 3 1 1 + *06 1 1 + -04 1 9 + -05 17 - -12 Concentrated Milk. 9 9 + -07 19 - *03 2nd <hod. - -07 1 9 - -01 1 1 - a 0 8 1 1 - *03 1 1 - *06 1 1 - *01 1 1 - -11 1 1 - -12 11 .- -09 1 9 - -07 19 - a14 11 - *09 1 1 - -15 11 - -06 - 9 9 - -07 9 1 - -10 1 1 - -05 1 1 + -02 11 + -05 9 9 + -16 3rd Period. + -05 9 9 + -04 11 + -12 1 9 + -14 7 1 + -11 1 9 + -06 1 9 - -12 11 - -07 9 1 + -07 9 9 + -11 11 + *07 ) ? - $ 80 THE ANALYST. G. 57. 31.3 58. 31.3 59. 28.7 60. 32.0 61. 31.9 62. 32.0 63. 31.8 64. 32.2 65. 32.2 66. 33.3 67. 33.3 68. 334 69. 31.5 70. 7.2 71. 32.0 72. 33.0 73. 32.0 74.32.6 75. 32.6 76. 32-7 77. 32-4 78. 32.4 79. 33.5 80. 31.6 81. 29.6 82. 33-5 83. 29-7 84. 32.3 85. 33.2 86. 33.3 87. 32.3 88. 31.2 89. 33.5 90. 34.2 91. 33.5 92. 33.5 93. 33.1 94. 32.8 95. 32.4 96. 31.5 97. 33.9 98. 33.8 99. 32.9 100. 32-5 101. 32.2 102. 32-1 103. 32-5 104. 28.9 105. 33.5 106. 30.0 G. E 30.35 30-35 27.9 31.0 30.9 31.0 30.8 31.2 31.2 32-2 32.2 32.3 3055 7-15 31.0 31.0 31.55 31.55 31.65 31.4 314 32.4 30.65 28.75 32.4 28.85 31.3 32.15 32.2 31.3 30.25 32.4 33.05 32-4 32-4 32.05 31.75 31.4 30.55 32.8 32.7 31-85 31-5 31-2 31.1 31.5 28.1 32.4 29.1 31.~95 T. 12.47 12.53 9.72 12-67 12.61 12.69 12.89 12.39 12.42 12.84 12.82 12-10 11.54 32-50 13.35 13-23 13-21 12.06 13-07 12.61 12-92 13.17 11-83 15-40 11.30 11.27 15.00 12.68 12 -03 12-44 11.93 11-30 12.66 12.93 12-20 11.83 11.30 13.05 12.26 12.71 10-54 11.21 12.41 12.49 11-97 12.13 12.04 15.01 11.27 11.37 F.F. calc. Difference. 3.76 3.75 -so1 3.77 3.80 +so3 2.05 2.00 - -05 3.75 3.77 - *02 3.73 3.75 +.02 3.77 3-79 + .02 3.93 4.01 +so8 3.53 3.50 - -03 3.49 3.52 +so3 3.64 3.66 +a02 3.59 3-64 + -05 Remarks. 3rd Period. SERIES 11. 3.05 3.02 .- *03 2.85 2.93 +.06 25-67 25.55 - *I2 Carter Bell's Method. 4.34 4.32 - '02 4.08 4.03 - -05 4-17 4-22 +*05 4.08 3.99 -*09 3.48 3.58 +*I0 3.84 3.91 + -07 2.76 2.77 +*01 3.02 3-12 +*lo 2-22 2.30 + a 0 8 3.76 3.72 -04 3.16 3-15 - -01 4-15 4.12 -so3 6.19 6.12 -*07 6.32 6.19 - * I 3 3.03 3.00 - -03 3.35 3.32 -so3 3.11 3.10 -*01 2.98 2.80 - -18 3.56 3.47 - *09 3.68 3.55 -*I3 3.24 3.09 - *I5 2.79 2-78 - a 0 1 2-35 2-41 +*03 3.85 3-93 + -08 3.43 3.36 -a07 4.02 3-91 - *I1 1.44 1-61 +.17 2.26 2.19 -*07 3.39 3.37 -*02 3.50 3-52 +*02 3.18 3-15 - '03 3.26 3.31 +so5 3-06 3.15 +so9 6.21 6.36 +*15 2-32 2.31 -so1 2-93 3.11 +*I THE ANALYST.81 Total Solids per cent. ti. Specific Gravity at 15.55" C. 107. 33.0 108. 32.0 109. 30.5 110. 32.5 111. 28.0 112. 29.4 113. 28.6 114. 35.6 115. 33.3 116. 36-0 , I 9.280 8.758 8.318 7.777 7.456 6.455 I '+ G.1>. 31.95 31.0 29.6 31-5 27.25 28.55 27.8 34.4 32.2 34-75 1.03544 1 -03343 1.03170 1,02950 1.02829 1.02439 T. 11.49 12-24 12.14 11-68 10.63 11.84 11.62 11-64 10.57 9 -45 F. F. cnlc. 2.65 2.58 3.51 3.42 3.64 3.65 2.82 2-85 2-72 2.90 3-50 3.62 3.53 3.60 2.26 2-18 1.60 1.77 -27 -27 Difference. Remarks. - -07 - -09 - -01 + -03 + -18 + -12 + -07 - -08 + -17 G D The formula deduced from these determinations was T = -2625- + 1.2 F. I t is hardlynecessary to state that the maximum specific gravity was used in the calculation. I n this formula it has been assumed that the specific gravity of butter fat at 15-55' C. is -93 and not -94 which was deduced from previous work (cf. ANALYST, xiv.121). A formula was also calculated using -94 as the specific gravity of butter fat but the agreement with this latter formula was not quite so good. It is evident that the figure -94 is not accurate though possibly it is correct for the fat extracted by the less accurate methods hitherto used. The form of formula adopted assumes that the influence of 1 gramme of solids-not-fat dissolved in 100 C.C. is a constant-ie. that milk may be regarded as a mixture of water fat and solids-not-fat. It is well known however that few substances con form absolutely to this law. To show that in milk this law holds with practical exactitude I quote the results of an experiment performed some years ago and published in a different form in THE ANALYST xiv. 127. A poor separated milk was diluted and the total solids and specific gravity estimated in the various mixtures.Influence of 1 grm. of Total Solids per 100 C.C. on Specific Gravity. 1 3.688 3.693 3.694 3.684 3-690 3.688 Average 3.6895 rt.0033 From the probable error of the methods used I calculate that the probable error should be about -1 per cent. of the absolute value while the probable error found is a09 per cent. This shows that the law holds with milk within the limits of error of the methods of analysis. I n Series 1 I have divided the estimations into four periods-&. November t 82 THE ANALYST. January February to April May to July August to October-and I find the average error in each of these periods to be as follows : I 1st Deriod -I t is remarkable that in the previous year when the method was not quite the same and the milk scale was used that the differences were : 1st period -- -04 { z: : + *07 4th , +*02 Whether the fact that fats calculate low in the spring and high in the summer be due to a difference in the coinposition of the milk or some unknown external condi-tions cannot be decided; as practically the same differences have been observed for two successive years it is probable that this is not a purely accidental occurrence, and it may reasonably be expected to occur again.There is some evidence that it occurred in 1889 as I then calculated a formula T= 963- + 1.17 F using methods but little different from the present one which gives results differing about -07 to -08 from the present one; and the work on which thie was based was all done in the spring-k in the second period.In 135 samples of genuine milk the ash has been determined and the ratio to 100 parts of solids-not-fat calculated. G D Solids-not - fa 5. 9.4 9.3 9.2 9.1 9.0 8.9 8.8 8.7 8.6 3.5 8.4 8-3 8-2 8 -1 8.0 7.7 Nc. of Samples. 1 1 4 1 2 23 27 21 8 4 7 7 5 6 6 2 1 -__ ~ ~ _ _ _ Ratio of Ash to 100 Solids-not-fat. Limits. 8.0-8.4 7.9-85 7 '8-8 *4 7.9 -8.5 8 *O -8 '4 7.9-8.8 8-0-8-6 8.1-8.7 8.3-8.7 8 *5 -8.9 8.6-9.0 8.8-9.4 8.8 -9 -3 Average. 8.5 8.1 8.2 8.2 8.15 8.2 8.3 8.3 8.4 8-5 8.7 8.9 9.0 9.0 9.1 $2.0 " Y In all these cases the ash was determined with the utmost care frequently in a muffle but never at a temperature above a very dull red THE ANALYST.83 A considerable proportion of these have been found with an alkaline reaction to both turmeric and litmus paper and phenolphthalein; in some the alkalinity has been determined and a maximum amount of *025 per cent. calculated as Na,C03 has been found ; in some samples a slightly fuller examination has been made. Soluble Ash. a26 -24 *2 8 Insoluble Ash. -.025 I *020 ,205 1 -152 42.5 31.7 1 *012 I {it::} 1 *226 { %3 ] 41.1 The soluble ash contained only the merest traces of phosphates less than *005 per cent. P,O,; it consisted of chlorides of the alkalies and the carbonates to which the alkalinity was due ; the insoluble ash consisted of a double phosphate of the formula (Ca,Mg) (K,Naj PO, analogous to the carbonates sulphates and borates of calcium and the alkali metals.The figures calculated for a calcium potassium phosphate are CaO 32.2 and P,O 40.5 and for a calcium sodium phosphate CaO 35.4 and In Nos. 2 and 3 the amount of magnesium was very small and was not estimated ; in No. 4 the magnesium estimation was lost but it was seen to be much larger than in the others. I t is well known that the ash of milk does not represent the salts present therein, but includes phosphoric acid produced by the oxidation of the phosphorus of the casein which displaces the carbonic acid formed on igniting the organic salts of milk. A very important paper by Soldner (Lnndzu. Versuchstat. xxxv. 351) which has not yet been properly appreciated has greatly elucidated our knowledge on the subject.He shows that the phosphates present in milk are to a certain extent acid phosphates and to these in part is the acidity of milk (to phenolphthalein) due. Milk when fresh and in many cases for some time after reacts alkaline t o litmus. Among the salts the presence of which is established in milk and which react alkaline to litmus are citrates and phosphates of the formula M,HPO,; the practice of cal-culating the acidity of milk to phenolphthalein as lactic acid is not therefore correct; and indeed milk freshly drawn has an acidity (calculated as lactic acid) of -1 per cent. or more. With reference to the presence of nitric acid in milk when a cow has been dosed with small proportions of nitrates I thought it desirable to definitely ascertain if the use of water containing nitrates would produce the same effect.After a considerable amount of trouble I succeeded in obtaining samples of milk yielded by cows accustomed to ‘drink water containing 18.0 parts per 100,000 of nitric acid (as NzOs) ; these samples gave a strong diphenylamine reaction. My previous failure to find nitric acid is due to the fact that it is a sine qud no32 that the water on all the farms supplying the company shall be unpolluted and therefore contain nitric acid in P,O 44.9 84 THE ANALYST. only small amount and that this provision is enforced is shown by the large number (91) of water samples analyzed. A few experiments were made as to the loss of water experienced on keeping butter samples A quarter-of-a-pound sample was taken immediately after churning and analyzed at once the sample was then kept under various conditions and reanalyzed.As examples I may quote : Fresh samples 14.64 % of water ; after two days in an open basin 12.12 % 9 9 14-87 , 9 , ten days wrapped in single paper 13.99 % 9 , 13-10 9 I 9 , 9 9 7 double , 11.93 % With a view of studying the connection between the quality of milk yielded by cows and external conditions I have noted this year the temperature of the air and I find that it is a general rule that sudden rise of temperature causes a milk of poorer quality to be produced while a sudden fall has the opposite effect ; should however, the temperature continue low or high the quality of the milk gradually returns to its normal level.There seems to be some evidence that the quality of milk is improved by changing the food from time to time but that the effect on the quality of the milk is not permanent. The fact that a change is made in the food seems to have more effect than the particular food given; the evidence on this point is however by no means conclusive. It is usually accepted as a fact that cream contains a larger proportion of solids-not-fat to water than the milk from which it was derived ; and the increase of solids-not-fat is said to be due to the fat globules taking up a larger amount of proteids than the proportion deduced from the ratio of proteids to water in milk. This has been used as an argument as to the presence of an albuminous membrane round the fat globules.I have however been led to doubt that this is the case and have obtained results which point to the ratio of solids-not-fat to water being the same in creani as in the milk from which it is derived. The method of analysis which I adopt has been previously described by Dr. Vieth (ANALYST xvi. l) but as it will be necessary to discuss one or two points, I describe it again in more detail. The sample for analysis is well mixed and about 5 grammes are weighed into an eight-ounce flat-bottomed conical flask ; this is placed in an air-bath at looo and is shaken slightly at intervals of fifteen minutes till it is apparently dry which takes about one hour; it is then placed on its side so that the fat shall run away froin the solids-not-fat and left in the air-bath for about four hours.I find that drying beyond this time does not decrease the weight but rather increases it. A second portion of 3 to 4 grammes is placed in a platinum basin and this is left in the air-bath for five hours when the minimum weight is obtained. The two results have only differed by more than *1 per cent. in two cases out of forty-viz. -11 per cent. and 45 per cent. The sample in the basin is used for the ash determination; the flask is partially filled with ether (about 30 c.c.) and this is gently boiled and allowed to stand for fifteen minutes and decanted a second quantity of ether is then poured in and the flask corked and allowed to stand till the following day during which about six more washings with ether are performed I THE ANALYST.85 is then allowed to stand again for a night and a further two or three washings are given ; the solids-not-fat are then dried to constancy (about four hours) and weighed. I n a few cases the ether has been evaporated and the fat weighed; the weights of the fat and the solids-not-fat do not differ by more than a milligrainme or two from the weight of the total solids. I n some cases the solids-not-fat have been ground up with a small pestle in the flask and the ether filtered through a small tared filter ; but I do not find that this method is much better than the other. In some cases the fat has been estimated by the Adams or Werner-Schmid methods and the fat estimated this way and the solids-not-fat add up slightly below the total solids.I heated in the same bath about 2 grammes of anhydrous butter fat (i.e. shaken with a considerable proportion of calcium chloride a t about 50" C. and filtered) ; the heating was continued for six days but I need only quote one or two results here : The reason for this is not far to seek. Time of Heating. Percentage on Original . . . 1 4 hours 100.17 164 9 ) . . . 100.73 2og , . . . 100.81 As cream contains say 50 per cent. of fat the increase on heating four to five hours will not be quite negligible and may be estimated at *1 to -2 per cent. on the weight of the cream ; and therefore the solids-not-fat determined by the difference between total solids estimated by drying for a long period and fat estimated by methods in which the drying at 100" C.does not exceed fifteen to twenty minutes, will be increased by this amount. I n the method that I have adopted there is a possibility that the extraction is not quite complete ; and on the other hand though the greatest care was exercised in decanting the ether it being done over a black surface so that any solid particles going away with the ether might be seen there is a possibility of loss in this way. I was however not able to observe any de_posit in the decanted ether. In the following analysis the solids-not-fat have been calculated on the assuniption that the ratio of the solids-not-fat to water was 10.2 to 100 which I have found to be the mean proportion in the milk which is generally used for the production of cream except in No. 2 which was prepared by the shallow setting system and the milk previously submitted to analysis the ratio being 10.0 to 100 ; all the other creams were separated : No.1. . 2. . 3. . 4. . 5. . 6. . 7. . 8. . Total Solids. 32 -50 37.59 50.92 55 -05 55.18 55.97 56.37 57.99 Solids-not-Fat. S. n. F. Calculated. . 6.83 . 6.90 . . 6.14 . 6.24 . . 5.02 . 5-01 . . 4.65 . 4-59 . . 4.77 . 4.57 . . 4.47 . 4.49 . 4.40 . 4.45 . . 4-17 . 4.25 . Average Difference . Difference. + *07 + *lo - -01 - -06 - .20 + *02 + -05 + -09 + 91 In one cream No. 1 a proteid estimation was made acd 2.60 per cent. was The mean proportion of proteids to found or 38.1 per cent. on the solids-not-fat. the solids-not-fat in milk is according to my estimate 38.6 per cent 86 THE ANALYST.The ash has also been determined and the results compared with that calculated on the assumption that it is one-twelfth of the calculated solids-not-fat : No. 1. 2. 3. 4. 5. 6. 7. 8. Ash. . *57 . *52 . -42 . *38 . *39 . *38 . -38 . *41 Ash Calculated. . *57 . -52 . -42 . .38 . -38 . -37 . *37 . -3 G Difference. - . - . - . - . . - -01 . - *01 . - -01 . - -05 Except perhaps in the last case the agreement is everything that can be desired. As lack of time has prevented my making as extensive a series of determinations as might be desired I cannot say that the statement that cream contains a higher proportion of solids-not-fat than milk is incorrect but the whole of the evidence that I have obtained points in the direction contrary to that generally assumed I t seems probable that this statement arose from the fact that solids-not-fat determinations were made by difference the total solids being too high from an increase of weight of the fat on drying and the fat possibly too low owing to a method which gives an incomplete extraction being used (e.g.Soxhlet’s method) which I have shown and Vieth has confirmed my observation to give too low results. Cf. ANALYST xiv. 123 ; and xvi. 203. I have dwelt at length on this subject as were it true that cream contained a higher,proportion of proteids a field of investigation would be open to see if the cor-responding deficiency of proteids might be utilized in the detection of separated milk as an adulterant ; but I have now little hope of such being the case and indeed in a few experiments I have found no deficiency of solids-not-fat or proteids in separated milk.An analysis of the slime found on the inside of the drum of a cream separator has been made ; its composition was : Total solids . .*. . . 33.76 Fat . . . . 650 Milk-sugar . . . (about) 3 0 Casein (or analogous body) , 22-00 Ash . . . . . 3.01 Soiubie ash . . -166 containing CI . . *008 Insoluble ash . . 2.844 , Silica -171 Fe,O,Al,O,’ ,012 CaO . -654= -675 eq. MgO . .225= -325 eq. Alkalies . . -559 P,O . 1-233 = 1.506 eq. The portion returned as casein was that part soluble in dilute alkalies and pre-cipitated by acids. The ‘ I silica ” was the portion insoluble in hydrochloric acid on evaporation.It is seen that the insoluble ash (minus silica iron oxide etc.) has the same general composition as the insoluble ash of milk (see ante)-i.e., (Ca,Mg) (Na,K) PO, THE ANALYST. 87 There are 1.506 equivalents of P,O (1 eq. =J+) for each equivalent of CaO and MgO present (1 eq. CaO = :f$ 1 eq. MgO =-+$!-’-, and this fact alone furnishes a strong argument that this slime is not (though it contains) the dirt in the milk and that it is a true milk product. The ash was absolutely neutral (litmus and phenolphthalein) in reaction. DISCUSSION. Mr. Otto Hehner said that Mr. Richmond had extracted much interesting matter from a subject which had been very often discussed before. Sooner or later the Law Courts would have to decide the question as to whether butter was a perish-able article or not.For the purposes of analysis butter could hardly be called a perishable article as it could be reliably analysed when many months old. Much of the confusion that had arisen from the conflicting statainents of different observers-some of whom said that the percentage of insoluble fatty acids would not materially alter on keeping the samples others that they decreased-was due to the fact that some analysts kept the butter entire othera the butter-fat. He was surprised that Mr. Richmond had not found any carbonates in his niilk-ashes. He would rather have expected that there would have been a notable quantity. I n sweetened con-densed milks a deposit was generally observed which consisted largely of calcium citrate and which yielded on incineration calcium carbonate. He [Mr. Hehner] would like Mr. Richmond to state the lowest solids-not-fat which he had obtained. Mr. Richmond in reply said that he could hardly give Mr. Hehner the lowest solids-not-fat because the samples which he believed were perfectly genuine were not samples which were strictly authenticated in the legal sense. All the samples low in solids-not-fat were however abnormal in composition. With regard to the absence of carbon dioxide in the ash of separator-slime it was not exactly the same thing as in the case of the deposit found in condensed milk because it should be remembered that the condensed milk had been heated to a certain degree and calcium citrate was known to be more insoluble in hot water than cold. In the ash of milk itself there was a small quantity of carbonic acid in a considerable number of cases. He had mentioned that in the soluble ash there was sometimes carbonic acid to the extent of 0.025 per cent. NaCO, and beyond that there was also a little carbonate in the insoluble ash. With respect to Mr. Hehner’s remarks as to how difficult it was to wash milk-ashes he thought a very possible explanation was that the alkali existed there as calcium-sodium-carbonate. He wished to mention that although the paper was in his name the bulk of the analytical figures were the work of his assistant Mr. Boseley. [NOTE.-In a recent number of the Comptes Rendus there is a paper on the pre-paration of double carbonates of potassium and sodium with calcium barium and strontium and they are described as well-defined crystalline compounds of limited solubility.-H. D. R.