274 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS extracted was very hygroscopic and it was necessary to surround the planchet with silica gel to prevent moisture absorption during the counting period. A self absorption curve was determined using 0.05t• curie and 0.005t• curie •4C tyrosine with varying amounts of tyrosine hydrochloride, plated and counted under the same conditions. A straight line was obtained when log activity was plotted against weight taken, over the range 10 to 70 mg. The weight of material eluted from about 1 g hair was usually in the region of 20-30 mg, consequently it was considered that the counts could be corrected, by means of the self absorption curve, to a constant weight of 20 mg for comparison. The counts were corrected further by equating to unit weight of hair. Two methods of establishing controls were considered: (1) The major tress would be cut in pieces of fixed length, some of which could be used as controls, and (2) the maior tress would be divided into sub-tresses, two or three of which could be used as controls. This latter method was the one used in the preliminary experiments. In the first method a tress of hair 12" in length and 12 g in weight was used and in which the individual hairs were of equal length. It was tied 1_,, from the root end, the other end being accurately clubbed. After washing in 200 ml shampoo containing •4C tyrosine (32/• curies) the tress was cut into 1 in. lengths from the clubbed end, and the lengths weighed. The pieces of hair were extracted and the eluted materials counted and corrected as described (Table 1). Table 1 5ORPTION OF 14C TRYOSINE ALONG THE LENGTH OF A TRESS A 12 g 12" length tress of hair washed in 200 ml shampoo containing 32ix curies •4C tyrosine. 1" lengths were cut and •4C tyrosine eluted and counted. Activity was corrected to constant weight of eluate and unit weight of hair. Activity (counts/ Inches from root end min./g (hair 1 2 3 4 5 6 7 8 9 10 Tress 1 1,613 1,136 1,052 1,015 999 1,047 1,083 1,110 1,200 957 Tress 2 1,249 -- 881 832 825 863 820 735 759 824 It is apparent from the results obtained (1) that the sorption is not uniform along the length of the hair, the results tending to lie on a parabola, and (2) that the sorption is not consistent from tress to tress. The high results obtained from the first two inches is obviously an end effect, the irregularities at the tied end could be due to irregularities in the washing technique enhanced by the bunching of the hairs. It was obvious that this method could

THE SORPTION OF AMINO ACIDS FROM SHAMPOOS ON TO HAIR 275 not provide a suitable control. The hair tress would be too small for further treatment, after the removal of the first two inches to eliminate the end effects and then the removal of the control pieces. In the second method, the technique was modified in the light of the above end effects. The sub-tress was made of about 2 g hair, the major tress consisting of six such tresses tied together at the root end. The hair was shampooed, rinsed and dried in the manner described using 200 ml shampoo solution containing 32½ curies •4C tyrosine. The sub-tresses were then separated from one another, and after discarding 2" lengths cut from the free ends, the next 6" lengths (approx. 1 g in weight) were taken for the elution of the sorbed •4C tyrosine (Table 8). Table 2 8ORPTION OF 14C TYROSINE WITHIN A TRESS A 12 g 12" length tress of hair was washed in 200 ml shampoo solution contain- ing 32/• curies •4C tyrosine. The tress was divided into six sub-tresses of 2 g after which 2" was cut from the tip end of each sub-tress and the next 6" (1 g) taken for elution and counting as in Table 1. Sub-tress 1 2 3 4 5 6 Mean -- Tress 3 1,080 986 1,388 1,311 1,170 1,137 1,170 149 Tress 4 940 891 1,046 988 1,287 926 1,013 145 * •- Best estimate of the standard deviation. Though large variations occur between sub-tresses, as seen from Table oe, this method can be used to show major differences between treatments, such as those known to occur from the preliminary experiments. Another major tress, made up of 6 X 2 g sub-tresses, was shampooed, rinsed and dried, using 200 ml shampoo solution containing 32/z curies tyrosine. 3 sub-tresses were then separated and used as controls. The remaining 3 sub-tresses, having had 2" lengths cut off from the tip ends, were re-washed in 100 ml shampoo containing no added x*C tyrosine and worked up in the manner described, together with the controls (Table 3). Table $ DESORPTION OF 14C TYROSINE BY A PLAIN SHAMPOO SOLUTION FROM HAIR Conditions as in Table 2. Sub-tresses 4 to 6 re-washed in 100 ml shampoo containing no added x4C tyrosine, then cut, extracted and counted as in Table 2. Control Re-shampooed Sub-tress Number 1 2 3 4 5 6 Activity (counts/min./g hair) 768 749 781 487 555 403 Mean 766 482 r•-* 14 68 * •- Best estimate of the standard deviation.